202 BULLETIN 10 0, UNITED STATES NATIONAL MUSEUM 



Pleuracromylon Giix, Proc. Acad. Nat. Sci. Philadelphia, 1864, p. 148. (Type, 



Mustelus laevis Risso, orthotypic.) 

 Cynias Giix, Proc. U. S. Nat. Mus., vol. 25, p. 960, 1903. (Type, Squalus canis 



Mitchill, orthotypic. ) 

 Cynais Fowleb, Proc. Acad. Nat. Sci. Philadelphia, 1908, p. 55. (Type, Squalus 



canis Mitchill.) (Error.) 



Body slender, nearly long as tail. Head short, depressed, wide, 

 tapers in front, wider and flattened below. Snout long, depressed, 

 produced, and rounded. Eye large, ellipsoid, lateral, lower lid with 

 nictitating fold. Mouth crescentic, subangular, rounded anteriorly, 

 labial folds well developed. Teeth small, numerous, polyserial, flat, 

 smooth or with shallow notches or low cusps, rhombic, pavementlike, 

 alike in jaws. Nostrils large, well separated, without groove to 

 mouth, front valve produced in outer angle. Spiracle small, close 

 behind eye. Dorsals alike. First dorsal large and above abdomen, 

 close behind pectorals, second dorsal above anal, which smaller. Tail 

 nearly straight, lower lobe almost obsolete, without pits. Pectorals 

 large. 



Small sharks found in most cool seas, their food usually crusta- 

 ceans, mollusks, and small fish. They have been divided into two 

 groups, based on the presence or absence of the placental attachment 

 in the embryo. This has evidently evolved by means of vascular 

 folds of the umbilical sac of the embryo attaching with membranes 

 lining the so-called uterus. This then functions as a sort of pseudo- 

 placenta in which nutritive matter is diffused with maternal blood to 

 the foetus, as in higher animals. 



Cynias kanekonis Tanaka * is described in Japanese. 



ANALYSIS OF SPECIES 



a\ Pleuracromylon. Coloration usually uniform, without spots. 



&\ First dorsal origin behind inner pectoral origin lenticulatus 



y. First dorsal origin opposite inner pectoral angle; teeth without extended 



cusp, slightly concave on inner edge antarcticus 



&^ First dorsal origin forward of inner pectoral angle ; teeth with notches or 



denticles canis 



o^. Mustelus. Coloration variegated with dark or light spots. 

 c\ Usually spotted with white. 



d^. First dorsal origin above inner pectoral angle manazo 



dl First dorsal origin opposite pectoral axil mustelus 



c'. Usually spotted with black; first dorsal origin behind inner pectoral 

 angle punctulatus 



Subgenus Pleuracromylon Gill 



MUSTELUS LENTICULATUS PhiUippB 



Mustelus lentieulatus Phillipps, New Zealand Journ. Sci. Tech., vol. 13, p. 226, 

 1932 (t.vpe locality: Wellington Harbor). — Whitley, Mem. Queensland 

 Mus., vol. 10, pt. 4, p. 199, 1934 (reference). 



*Dobuts. Zasahi Tokyo, vol. 28, p. 26, 1916 (type locality: Japan). 



