268 Memoir Sears Foundation for Marine Research 



spaced but usually not overlapping, their blades nearly horizontal, longer than broad, 

 usually with 3 ridges, the median very high and divided anteriorly, the lateral margins up- 

 turned, the posterior margin with a short, broad median tooth, usually flanked by a pair of 

 very small teeth, but sometimes by one only; pedicels very short; basal plates very broad, 

 distinctly 4-rayed. 



Head flattened above, nearly or quite as broad opposite front of mouth as at origin of 

 pectorals. Snout very broadly rounded, noticeably short, its length in front of mouth a little 

 less than % of length of head to origin of pectorals. Eye broadly oval, its horizontal 

 diameter about V2 as long as snout in front of mouth, its center a little anterior to mid- 

 height of mouth. Spiracle a narrow but easily visible slit, Vs to Yi as long as horizontal 

 diameter of eye and behind the latter by a distance a little greater than Yo the diameter 

 of eye. Gill openings about evenly spaced, the 2nd, 3rd, and 4th (slightly the longest) 

 a little more than V2 as long as snout in front of mouth, or about 1.2 times as long as diame- 

 ter of eye, the ist and 5th the shortest, the 4th over origin of pectoral. Nostril nearly trans- 

 verse, its inner corner about equidistant between tip of snout and front of mouth. Its ante- 

 rior margin expanded at the Inner end as a low triangular lobe with rounded apex. Mouth 

 broadly ovate, a little more than V2 as high as broad, occupying between % and % of 

 breadth of head, lateral (not inferior) for most of Its length. Upper labial furrow as 

 long as snout in front of mouth or a little longer, extending forward to a point about oppo- 

 site anterior edge of eye. Lower labial furrow, a little less than Yo as long as upper, 

 approximately parallel to lower jaw. 



Teeth ^ to Ij-EJEif ii^ specimens examined; very large In front and sides of jaws 

 (up to an Inch or more high In large specimens) but decreasing In size toward corners 

 with the outermost very small, similar in the 2 jaws, about V2 to % as high as broad, 

 their inner outlines convex, their tips directed obliquely outward, their outer margins with 

 a deep primary notch; both edges serrated, very finely so near the tip which may be worn 

 smooth, but more coarsely so toward the base, especially on the outer margin basal to the 

 notch, where the primary serrations are themselves finely serrate secondarily along their 

 edges. There may or may not be a small symmetrical tooth at the symphysis of either jaw 

 (Fig. 44 E) ; If this Is lacking the tooth next to the symphysis In the upper jaw Is usually 

 considerably smaller than the 2nd and subsequent teeth, on either one side or on both, 

 though similar to them in shape. 



Anterior margin of ist dorsal about Y2 as long as from snout to axil of pectoral, Its 

 origin over or a little posterior to the latter, Its anterior edge very slightly convex, its 

 posterior margin deeply concave, its apex narrowly rounded, the free rear tip slender, 

 about % as long as base. Second dorsal about V2 as long as ist at base, but a little less than 

 Ys as high vertically, its anterior edge more sloping. Its free rear tip more narrowly 

 acuminate and relatively longer (about as long as base). Its origin a little anterior to origin 

 of anal. Caudal a little less than Ys of total length, with very slender pointed tip and deep 

 subterminal notch, its lower anterior corner expanded as a narrow sharp-pointed lobe. 



