200 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



Mitsukurina owstoni, sp. nov. 

 Plates XI and XII. 



Length of specimen, a male apparently young, 42 inches. Head (to first 

 gill-opening) 43- in length; depth about 10. Snout from eye if in head; from 

 front of mouth t\ in head; length of blade of snout from its insertion below 

 if in head. Length of gill area 2$ in head; depth of last gill 6 in head; eye 

 12 in snout from eye; interorbital area 2§ in snout from eye; spiracle a little 

 smaller than eye; length of one mandible 2§ in head; length of maxillary 2f 

 in head. Pectoral base if in length of pectoral fin, which is 2§ in head. 

 First dorsal base if in its height, which is 2! in head. Second dorsal base 

 i| in its height, which is 3 in head. Ventral base 2 times its height, the 

 length of the base being 3 in head. Claspers very short (perhaps immature), 

 nearly 12 in head. Anal base i\ times its height and 2* in head. Caudal 

 measured from above 2f in length of body; greatest height of lower lobe 

 nearly 3 in head. 



Body elongate, compressed behind, the flesh and skeleton extremely limp, 

 folding like a wet rag; head moderate, the snout produced in a long, flat, 

 flexible, leaf-like blade, somewhat like that of Polyodon spathula but arrower, 

 more limp and more pointed; median line of snout with a thick, rounded, 

 median keel; the lower side of the blade free for a considerable distance 

 backward from the upper jaw, almost to the eyes. Mouth inferior, with 

 elongate cleft; the dentary bones broad, loosely connected, and movable, 

 capable of being spread wide apart, but normally lying close together and 

 nearly parallel; a notch at symphysis, the tip of the lower jaw strongly curv- 

 ing upward and inward at tip; a similar notch at tip of upper jaw between the 

 rather loosely joined maxillary. 



Teeth few-rowed, about \\ on each side; middle of each jaw without teeth 

 in front. Teeth all needle-shaped, very slender and pointed, more or less 

 curved backward or inward; each tooth with a two-rooted base; the large 

 teeth in front simple, the smaller ones on sides of jaws each with two small 

 basal cusps; second and third tooth of lower jaw longest; the second about 

 as long as eye; first and second tooth of upper jaw similar to these but some- 

 what shorter; lateral teeth of both jaws progressively smaller, but all slender 

 and sharp. 



Eye small, without nictitating membrane; spiracle large; gill-openings 

 about equal in height, the last above base of pectoral. 



Skin everywhere rough, the scutes very small, granulated. No lateral line 

 or conspicuous mucous pores; nostrils large, about as large as eye, their 

 distance from eye twice the eye; each nostril with a small notch on lower 

 edge and a free flap within. 



Fins all thin, flexible, and papery; the broad bones somewhat exserted 

 from the soft flesh. Pectoral short, narrow, and rounded, the flexible rays 

 longest. First dorsal short and moderately high, not emarginate; second 

 dorsal lower, remote from the first, the interspace being i| in head. Inser- 

 tion of first dorsal above axil of pectoral; insertion of second nearly midway 

 between ventrals and anal. Ventrals with very long base; anal much longer 



