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6 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 20
ten different genera, including Septifer Recluz, Arcoperna Conrad, and
Adula Adams. Idasola is included in or made a synonym of Adula.
Lamy's work is very valuable, as he has made a thorough study of the
synonymy of most of the species and also mentioned species not preserved
in the Paris museum. Unfortunately he did not give diagnoses of the
various species and the soft parts were not taken into consideration. Some
of his conclusions may be wrong and some of his names not valid, but the
vast amou^ of knowledge presented through this paper will be of everlasting value to students.
Cox (1937) has written a very interesting paper on the Jurassic
mytilids with general considerations which should be read by students
working on the recent material. He describes Falcimytilus as a subgenus
of Mytilu^This group consists of species with terminal umbones but
without lunular grooves or teeth. Even if they should be the ancestors
of Mytilus s. I., I believe Falcimytilus should be given generic rank.
Newell (1942) has treated the late Palaeozoic Mytilacea mainly on!
American material. His extensive discussion of the shell characters andi
the origin and evolution of Mytilacea is very useful and interesting. He
describes the genus Promytilus and the genus Volsellina for mytiliform
and modioliform late Palaeozoic mytilids respectively. Unfortunately the
hinge and the muscle scars are not described.
The anatomy of several mytilids has been extensively treated by List
(1902), Pelseneer (1911), and White (1937), and notes about the
anatomy of different species can also be found scattered in the literature.
What are the charac^s which can be used in the classification of the
variable mytilid species ? As the major part of the mytilids have anteriorly
placed umbones and are rather alike in form, this resemblance is not
necessarily a criterion for the closer relationship of similar appearing
species. The same form could easily have been acquired by different]
evolutionary lines, but it must be possible to prove or disprove this by
a closer study of other characters and especially by following these char J
acters through the fossil forms. Unfortunately very few characters are
preserved in fossils and our knowledge of most of file recent speciej^lfe
still poor. It is, therefore, extremely difficult to tell which characters are
more important than others and how the various species groups can be
placed in relationship to each other. In this paper, therefore, many small
groups are treated as genera; they probably will find their proper places
in the system in the future.
The characters used for classification should, as far as possible, be taken
from the shell and from easily visible parts of the anatomy, such as the
mantle margin, foot, byssus, etc. One character which is supposed to be
Object Description
Description
| Title | AHF-PUB-PE-20-01~018 |
| Type | texts |
| Format (imt) | image/tiff |
| Contributing entity | University of Southern California |
| Filename | AHF-PUB-PE-20-01~018.tiff |
| Full text | 6 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 20 ten different genera, including Septifer Recluz, Arcoperna Conrad, and Adula Adams. Idasola is included in or made a synonym of Adula. Lamy's work is very valuable, as he has made a thorough study of the synonymy of most of the species and also mentioned species not preserved in the Paris museum. Unfortunately he did not give diagnoses of the various species and the soft parts were not taken into consideration. Some of his conclusions may be wrong and some of his names not valid, but the vast amou^ of knowledge presented through this paper will be of everlasting value to students. Cox (1937) has written a very interesting paper on the Jurassic mytilids with general considerations which should be read by students working on the recent material. He describes Falcimytilus as a subgenus of Mytilu^This group consists of species with terminal umbones but without lunular grooves or teeth. Even if they should be the ancestors of Mytilus s. I., I believe Falcimytilus should be given generic rank. Newell (1942) has treated the late Palaeozoic Mytilacea mainly on! American material. His extensive discussion of the shell characters andi the origin and evolution of Mytilacea is very useful and interesting. He describes the genus Promytilus and the genus Volsellina for mytiliform and modioliform late Palaeozoic mytilids respectively. Unfortunately the hinge and the muscle scars are not described. The anatomy of several mytilids has been extensively treated by List (1902), Pelseneer (1911), and White (1937), and notes about the anatomy of different species can also be found scattered in the literature. What are the charac^s which can be used in the classification of the variable mytilid species ? As the major part of the mytilids have anteriorly placed umbones and are rather alike in form, this resemblance is not necessarily a criterion for the closer relationship of similar appearing species. The same form could easily have been acquired by different] evolutionary lines, but it must be possible to prove or disprove this by a closer study of other characters and especially by following these char J acters through the fossil forms. Unfortunately very few characters are preserved in fossils and our knowledge of most of file recent speciej^lfe still poor. It is, therefore, extremely difficult to tell which characters are more important than others and how the various species groups can be placed in relationship to each other. In this paper, therefore, many small groups are treated as genera; they probably will find their proper places in the system in the future. The characters used for classification should, as far as possible, be taken from the shell and from easily visible parts of the anatomy, such as the mantle margin, foot, byssus, etc. One character which is supposed to be |
| Archival file | hancockunpub_Volume22/AHF-PUB-PE-20-01~018.tiff |
