264 BULLETIN 10 0, UNITED STATES NATIONAL MUSEUM 



Teeth unlike in two jaws, upper raptorial, lower sectorial. Gill 

 openings moderate to narrow, entirely before pectoral. Spiracles 

 small, present. Scales uniform. Dorsals two, small, spine absent or 

 rudimentary. No anal. Tail short, without lateral folds or caudal 

 pits. 



Mostly small sharks, differing from the Squalidac chiefly in the 

 absence of fin spines. Many are widely distributed and the Arctic 

 Somniosus reaches a large size. Most are viviparous. 



ANALYSIS OF GENERA 



a\ Dalatiinae. Dermal armature fine or moderate shagreen, without scattered 

 tubercles; snout subconcave; teeth unlike in 2 jaws. 

 6\ Head subconic. 



c\ Second dorsal much longer than first Euprotomicrus 



c'. Second dorsal nearly equals first. 



d}. Second dorsal nearer pectorals Dalatias 



d"^. Second dorsal nearer ventrals Isistius 



&l Head depressed; eyes small; first dorsal small, behind pectorals. 



e\ Second dorsal smaller than first Heteroscymnus 



e'. Second dorsal larger than first. 



f. Teeth in both jaws entire Heteroscymnoides 



f. Upper teeth entire; lower teeth serrated Pseudoscymnus 



€^. Second dorsal equals first Somniosus 



a'. EcHiNOEHiNiNAE. Skin with scattered tubercles or bucklers; snout broad, 

 tapering; teeth alike in 2 jaws Echinorhinus 



Genus EUPROTOMICRUS Gill 



Euprotomicrus Gnx, Proc. Acad. Nat. Sci. Philadelphia, 1864, p. 264. (Type, 



Scymnus (Laemargus) la'bordii Miiller and Henle, monotypic.) 

 Squaliolus Smith and Radcuffe, Proc. U. S. Nat. Mus., vol. 41, p. 683, 1912. 

 (Type, Squaliolus laticaudus Smith and Radcliffe, monotypic.) 



Body elongate, fusiform. Head subconic. Snout short, subconic. 

 Eyes without nictitating folds. Mouth with deep straight groove at 

 each angle. Upper teeth small, subulate; lower large, compressed, 

 smooth edged, with sharp and somewhat oblique cutting edges. 

 Nostrils near snout end. Gill openings narrow, before pectorals. 

 Spiracles rather wide, behind eye. Scales uniform, minute, flattened. 

 First dorsal small, without or with small spine, behind pectorals and 

 second dorsal much longer, without spine. No anal. Caudal short 

 and deep. 



Indo-Pacific. 



ANALYSIS OF SPECIES 



a\ Dorsal insertion median bispinatus 



a^ Dorsal insertion premodian laticaudus 



EUPROTOMICRUS BISPINATUS (Quay and Gaimard) 



Scymnus Mspinatus Quoy and Gaimard, Voy. Uranic, Zool., p. 197, pi. 44, figs. 

 1-2, 1824 (type locality: Mauritius). 



