261 PROCEEDINGS OP THE ACADEMY OP 



Spinax acanthias? Dekay. 

 Acanthias americanus St. Syn. 254. 

 Squal is americanus Gill, Proc. Acad. 1862. 

 Hab. Eastern coast generally. 



CENTROSCYLLIUM M. and H. 



Centroscyllium Fabkioii M. and H. 



Squalus acanthias Fab. (not L.) 

 Spinax Fabricii Reinh. 

 Centroscyllium Fabricii M. and H. Plag. 

 Hab. Greenland. 



SCYMNOIDJE* Owen. 

 SOMNIOSUS Les. 



SOMNIOSUS MICROCEPHALUS Gill. 



Squalus microcephalus Bl. Schn. 135. 



Squalus borealis Scoresby, i. 358 ; xv. 3, 4. 



Scjmnus borealis Fleming, 166. 



Squalus (Scymnus) glacialis Faber, 23. 



Scymnus micropterus Val. Nouv. Mem. i. 455, pi. xx. 



Squalus norwegianus Blainv, F. Fr. 61. 



Scymnus (Laemargus) borealis, M. and H. 93. 



Dalatias (Somniosus) borealis Gray, 76. 



Somniosus microcephalus Gill, Cat. 



Somniosus brevipinna Les. 



Scymnus brevipinna Dekay. 



Leiodon echinatus Wood. 



Hab. Greenland to Cape Cod. 



It is probable, as indicated in my catalogue, that the S. brevipinna is not dis 

 tinct from S. microcephalus. 



RHINOIDJE Gill. 



RHINA Klein. 



Rhina Dumerili Gill. 

 Squativa Dumeril Lesueur, 

 Rhina Dumerili Gill, Cat. 

 Hab. New York ? 



Genus PLATYPODON Gill. 



Synonymy. 

 =Platypodon Gill, Analytical Synopsis of the order of Squali, p. 35; in An- 

 nals of the Lyceum of Nat. Hist, of New York, vol. viii. p. 401, 1861. 

 Carcharias (Prionodon), sp. Mailer and Ilenle. 

 Squalus (Prionodon), sp. Poey. 

 Isoplagiodon, sp. Gill. 



Body slender and fusiform in profile, tapering behind. 



Scales tricuspid, surmounted by three keels terminating with the cusps. 



* The family Seymnoidae is represented by five distinct genera. 



1. Scymnus. 



2. Isistius (Scymnus brasiliensis M. and H.) distinguished by its similar and posterior dorsals, 

 Ac. 



3. Somniosus. 



4. Euprotnmicrus {Scymnus Labordii M and H.) with teeth like Somniosus, but in moderate 

 number (c. 23) and very small first dorsal. 



5. Khinoscymnus (Scymnus rostratus Risso) distinguished by its dorsals, &c. 



[Nov. 



