ADDENDA TO MARSIPOBRANCIIII, ELASMOBRANCHII, ETC. C7 



Distinguished from T). lata by the shape of tlic snout and disk and 

 the keel on the tail, and from D. cciitnira by the straight margins of the 

 l)ectorals and the keel. 



One specimen secured at Acapulco, Mexico, by Prof. Alexander 

 Agassiz. One light-colored, reddish-brown specimen from Panama by 

 the Hassler Expedition. 



Length of body 11.5, tail 28, and width of pectorals 13.8 inches. 



Length of body of second specimen, 9.3, tail 21.5, and width of pectorals 



11.2 inches. 



Dasibatis centruea. 



Baja centrura Mitch. Trans. Lit. «t Phil. Soc. N. Y. i, p. 479. 



Trillion cenlnira Liusley, Sillimau's Airi. Jour. Sci. & Arts, 47, 1844, p. lUG. 



Tri/f/oii centrura Gill (name ouly). Cat. Fii^h. E. Coast N. xViuer. j). 34. 



Bisk quadrangular, about one-fourth wider than long. Anterior mar- 

 gins sinuous, concave opposite the eyes, convex toward the slightly pro- 

 tuberant snout and rounded outer angles ; posterior straighter, a very 

 little convex ; inner convex. Hinder angles blunt. Ventrals truncate, 

 with rounded angles. Tail more than twice as long as the body, much 

 compressed, rounded above, with keel and cutaneous expansion below, 

 with one or more strong serrated spines at the termination of the ante- 

 rior fifth of its length, rough on all sides with spines or tubercles. Till 

 half grown the young are naked: as they approach maturity broad 

 stellate-based, conical-pointed, irregularly-placed bucklers appear on the 

 middle of the hinder part of the back and on the top and sides of the tail. 

 Very large examples have the central portion of the back closely mailed 

 with small flattened tubercles. The bucklers bear more resemblance to 

 those of the Eajw, radlata and clavata than to the tubercles of pasHnaca, 

 hastata, or tuherculata. Mouth arched forward, with five papilhe. Teeth 

 in quincunx, blunt, smooth. Color of back and tail olive brown; light 

 to white below. ¥rom pastinaea, which this species resembles in shape, 

 it is distinguished by the tubercles, by the length and comi)ression of 

 the tail, and absence of all trace of keel or expansion on its upper side. 

 A young specimen measures. from snout to tail 13.8, length of tail 30.5, 

 and width of pectorals 17.5 inches. The largest specimen in the collec- 

 tion has a total lengtli of 10 feet 3 inches. Common south of Cape Cod. 

 Occasionally found northward. 



Dasibatis lata. 



(Garman, IHSO, Ball. Mus. Conip. Zoiil. vi, p. 170.) 



Disk quadrangular, one-fourth wider than long. Anterior margins 

 nearly straight, forming a very blunt angle at the snout, rounded near 



