(Phocoenid-related excerpts) (…)
This genus appears to have but one character to distinguish it from Phocaena, namely, the absence of a dorsal fin. I was unable to discover any peculiarities in the skull or the remainder of the skeleton which could be regarded as sufficient to warrant a separation from the latter genus. Is the absence of a dorsal fin a sufficient generic character? I believe that it is, or at least must be so regarded until we know more of the anatomy of Neomeris. The case is somewhat different from that of Leucorhampus, because in that genus we ﬁnd the absence of a dorsal fin correlated with certain characters in the skeleton. In Neomeris no similar correlation has been pointed out. On the other hand, the dorsal fins of the three species of Phocaena show no signs of degeneration and furnish us no steps by which to descend to Neomeris. It may be, however, that when the anatomy of Neomeris is known many new distinctions will be discovered. In the present state of knowledge I would adopt Professor Flower’s conservative course, and leave the genus to be sustained or set aside by later investigations.
Only a single species is recognized in the following pages, viz, N. phocaenoides (Cuvier).
The genus Phocaena is readily distinguishable from all the remaining genera of the family, except Neomeris, by the shape of the teeth. From the latter genus it differs in having a dorsal fin.
Professor Flower’s admirable diagnosis holds good for all the species, except, as I have already pointed out elsewhere,* for one observed in the North Paciﬁc by Mr. Dall, which I have named P. Dallii. In this species the number of vertebrae rises to ninety-seven or ninety-eight, and the dorsal ﬁn is falcate. In these characters the species shows affinity to Lagenorhyncus, but, on the other hand, the skull (the only portion of the skeleton preserved) is that of a Phocaena.
Putting aside the number of vertebrae and the form of the dorsal ﬁn, we still have in the form of the teeth, the shape and position of the pterygoids, the form of the premaxillae, and the presence of a dorsal ﬁn, sufficient characters for the differentiation of the genus.
I have elsewhere stated my opinion that the number of valid existing species of this genus is probably reducible to four, viz, Phocaena communis Lesson; Phocaena lineata Cope; Phocaena spinipinnnis Burmeister; Phocaena dallii True. P. pectoralis Peale, I have shown in another part of this work to be probably identical with Lagenorhynchus electra
Gray (p. 101). P. tuberculifera, Gray, was ﬁnally admitted by that author to be the same as P. communis Lesson. P. brachycion, Cope, and P. vomerina, Gill, have never been proven identical with P. communis, Lesson, but Professor Flower, in 1883, expressed the opinion that such was probably the truth, and I have myself reached that conclusion. As regards the identity of P. lineata, however, the material at command is scarcely sufficient to warrant any very positive assertions. The type-skeleton is missing and nothing but the painted cast remains, and it is evident that to base any conclusions upon the color of a painted cast alone is hazardous. Special dificulty attends the discrimination of species in this genus, because both the body as a whole and the skeleton are subject to great variations in proportions and details of form.
The characters drawn from the relation of the vomer to the palatines, which are employed by Professor Cope and Dr. Gill in the separation of the different nominal species, are valueless. To ﬁnd other characters is a task to which I have devoted my attention, but thus far without success. I am constrained for the present to look upon P. communis, brachycion, lineata, and vomerina as identical.
The species here recognized are, therefore, Phocaena communis Lesson, 1827; Phocaena spinipinnis Burmeister, 1865; Phocaena dallii True, 1885.