148 PROCEEDINGS OF THE ACADEMY OP 



given in the "Bulletin of the Museum of Comparative Zoology," hy Mr. P. 

 W. Putnam, in a "List of Specimens sent by the Museum to different Insti- 

 tutions," and in the Proceedings of the California Academy of Natural Sci- 

 ences by Dr. W. 0. Ayres.* The former enumerates the Triads semifasdata, 

 Girard, Triads Henlei, Putnam (= Rkinotriacis Henlei, Gill) and Acanthias 

 Suckleyi, Girard (= Sgualus Suckleyi, Gill.) Dr. Ayres has in one 

 article announced, very modestly and with scarcely a due appreciation of its 

 bearings, a startling discovery regarding the range of variation of dentition 

 in the Notidanoids, and in a subsequent communication, has informed us of 

 the discovery of a representative of the genus Alopias in the Bay of San 

 Francisco. 



Family ALOPECOID^E. 



Genus ALOPIAS, Raf. 



We are indebted to Dr. Ayres for tbe " Notice of the acquisition of a speci- 

 men of Thrasher," taken in the Bay of San Francisco. The species is a 

 very close representative of the Atlantic form Alopias vulpes, differing, how- 

 ever, in the proportions of the dorsal and anal fins, and in the position of 

 the branchial apertures ; the tail constitutes decidedly more than half of the 

 entire length. The specimen is about five feet in length." (Ayres, op. cit., 

 vol. iii. p. 66.) 



Dr. Ayres has abstained from naming this species, and it may be hoped 

 that the true differences between it and the Atlantic species will be exhibited 

 by the future nomenclator. The announcement of any difference in the posi- 

 tion of the branchial apertures from one not acquainted with the type, will 

 be viewed with much skepticism by selachologists. 



Family GALEORHINOIDsE, Gill. 



Subfamily MUSTELINE, Gill. 



Genus MUSTELUS, Cuv. 



This name may be reserved for the species distinguished by the anterior 

 position of the first dorsal fin and the unicuspid teeth of the jaws. The 

 Mustelus lavis of Miiller and Henle is consequently excluded, the first dorsal 

 fin being nearly midways between the pectoral and ventral fins, and the teeth 

 provided with a lateral cusp in addition to the usual median one ; the foetus is 

 also intimately connected with the uterus by means of a vitelline placenta, 

 according to Miiller and Henle, and is thus essentially distinguished from the 

 typical Musteli which resemble the other Galeorhinoids. That species is 

 therefore a peculiar generic type, and may hereafter be called Plewacromylon 

 lavis. 



If the rule now adopted by many of invariably retaining a generic name 

 for the first species mentioned is adopted, Galeorhinus will supplant Mustelus. 

 I am not yet, however, prepared to adopt that rule, and shall for the present 

 retain the name Mustelus. Galeus cannot be used for the genus typified by 

 the Squalus galeus of Linnseus, and if Galeorhinus, which has been retained 

 for it, should be shifted to Mustelus, a new name will be demanded for the 

 former ; as it is desirable that the change should be as slight as possible, that 

 of Eugaleus may be accepted. 



Mustelus californicus, Gill. 



The first dorsal fin commences over the terminal third of the inner free 

 margin of the pectoral fin, and its posterior point, though acutely prolonged, 

 ceases considerably in advance of the ventral fins. The anterior angle is 

 blunt, but not rounded. The second dorsal is similar in form to the first, 



* Proc. Cal. Acad. Nat. Sciences, vol. iii. pp. 15, 66. 



[May, 



