NATURAL SCIENCES OF PHILADELPHIA. 485 



brane notched at its inferior margin near the end and forming a triangular 

 lobe ; the inferior or basal lobe is moderate or small. 



Pectoral fins more or less falciform, rounded at the external angle, and with 

 the posterior margin subtruncated or sinuated and incurved to the inner angle 

 which is also rounded. 



Ventral fins inserted more or less behind the middle, oblong or trapezoidal, 

 rounded at the anterior angle and acute at the posterior. 



The family of the Galeorhinoidje as it has been now circumscribed, appears to 

 be a very natural group, all the types included therein agreeing in physiognomy 

 and general form, and for the most part differing from each other in details of 

 secondary value. The only characteristics of greater than generic value are the 

 more marked peculiarities of dentition, and the presence or absence of spiracles. 

 Miiller and Henle have attached much importance to such characters, and have 

 regarded them as distinguishing five families. As, however, none of those 

 characters are co-ordinate with others, the value assigned to them by those 

 biologists appears to be much greater than they merit, and scarcely even suffi- 

 cient to base subfamilies upon. The most important and trenchant variation 

 in the family is found in the dentition of the genus Mustelus as opposed to that of 

 all the other types. The latter may therefore be combined in one subfamily, 

 while Mustelus can be regarded as the type of a second one. The typical sub- 

 family of the Galeorhinince is then subdivisable into four minor groups equiva- 

 lent to families of Miiller and Henle, and only characterized by the various 

 combination of two characters. The following synoptical view will facilitate 

 the recognition of the several groups. 



I. Teeth compressed and trenchant Galeorhinin.e. 



A. Spiracles obsolete in adults. 



Teeth without lateral prongs Cynocephali. 



Teeth with one or two lateral prongs on each side Triasnodontes. 



B. Spiracles developed. 



Teeth with lateral prongs Scylliodontes. 



Teeth without lateral denticles Galeorhiui. 



II. Teeth flat and paved Musteline. 



Subfamily GALEORHININCE Gill. 

 Squalini | n _, , , m , , . , 



Tranodon'ini \^ ona P arie i Selachorum Tabula Analytica, p. 5. 



Caschariaj p. " 



Miiller and Henle, Systematische Beschreibung der Plagistomen, 

 pp. 28, 55, 57, 63. 



Gray, List of the Specimens of Fishes in the Collection of the 

 British Museum, part 1, Chondropterygii, pp. 40, 51, 52, 55. 



Triaenodontes 



Galei 



Scylliodontes 



Squaliana pt. 



Leptochariana 



Galeiana 



Triakiana 



Galeorhininae Gill, Analytical Synopsis of the Order of Squali, pp. 33,35. 



Teeth compressed and cultrate, smooth or serrated and with' or without 

 lateral denticles. 



Spiracles obsolete or of small size. 



Group SCYLLIODONTES Miiller and Henle. 



Scylliodontes Miiller and Henle, Systematische Beschreibung der Plagios- 



tomen, p. 63. 

 Scylliodontidoe Girard, Explorations and Surveys for a Railroad Route, &c, 



vol. x. Fishes, p. 362. 



Teeth scyllioid, or each one with one or two prongs on each side of the large 

 central pointed one. 



1862.] 



