14 SELACHII: SQUALI. — IV. 
Susotass SELACHII. (THE SELACHIANS.) 
This group, sufficiently defined above, includes two orders, the 
Sharks and the Rays, — marine fishes of large size, abundant in 
most seas. (Gr. aéAaxos, shark.) 
Orders of Selachii. 
a, Gill openings lateral. . . . 1 1 2 ee ee + «© )©6SQUALE, 4. 
aa. Gillopenings ventral. ». . 2 - 6 ep ww sw we Raa, 5 
Orprr IV. SQUALIE, (Tue Suarxs.) 
The typical sharks are elongate in form, quite unlike the skates 
in appearance. Intermediate forms connect the two groups so 
closely that the position of the gill openings is the only constant 
character by which the two orders can be separated. (Lat, a 
shark, from Gr. yadeds, allied to yadén, a weasel.) 
Notz. — The Sharks are mostly fishes of the high seas, and any of the 
larger Atlantic species may stray to our coasts. Besides those here described, 
the following have been at least once taken within our limits: — 
Echinorhinus spinosus (Gmelin), Cape Cod; Centrocyllium fabricit (Rein- 
hardt), off Gloucester; Centroscymnus cololepis (Bocage & Capello), Glou- 
cester; Pseudotriacis microdon (Capello), Long Island; Aprionodon tsodon 
(Miiller & Henle); Jsogomphodon limbatus (Miiller & Henle), Wood's Holl, 
Omitting extralimital families, we have the following analysis of 
Families of Squali. 
«. Pectoral fins moderate, without deep notch at base in fronts gill openings 5 
6, Anal fin wanting. 
ce. Dorsal fins each with a stout spine . 2... SquaLina, 4, 
cc. Dorsal fins without spine. . 1. 7. wwe, Somniosip, 5, 
bb. Anal fin present; both dorsals without spine, the first inserted before 
the ventrals. 
d, Caudal fin not lunate, the upper lobe very much longer than the lower, 
with a notch below, towards its tip; side of tail without keel. 
e. Last gill opening above base of pectoral. 
J. Tail moderately developed, not half length of rest of body; 
with nictitating membrane, ve 
g- Head kidney-shaped or hammer-shaped, much wider than long. 
Spnynnipa, 6. 
gg» Head normally formed. . .... GALonniNmat, 7. 
Jf. Tail very long, as long as rest of body; no nictitating mem= 
WG. «<4 eee ele He Ee wR ALornpa, 8 
