ADDENDA TO MARSIPOBEANCIIII, ELASMOBEANCIIII, ETC. 67 
Distiug'uished from i>. lata by the shape of tlie snout and disk and 
the keel on the tail, and from D. centrura bj" the straight margins of the 
pectorals and the keel. 
(Jne 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 centruka. 
Baja centrura Mitcli. Trans. Lit. & Pliil. Soc. N. Y. i, p. 479. 
Trijgon centrura Liiisley, Sillimaii’s Am. Jour. Sci. & Arts, 47, 1844, p. 166. 
Tnjyon centrura Gill (name only), Cat. Fish. E. Coast N. Amer. p. 34. 
Disk 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 ; i>osterior straighten, a very 
little convex ; inner convex. Hinder angles blunt. Yentrals 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 i)art 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 fiattened tubercles. The bucklers bear more resemblance to 
those of the Hajcv, radiata and clavata than to the tubercles of pastinaca, 
hastata, or tnhercidata. Mouth arched forward, with five x>apillm. Teeth 
in quincunx, blunt, smooth. Color of back and tail olive brown ; light 
to white below, rrompostbiacu, which this species resembles in shape, 
it is distinguished by the tubercles, by the length and comju'ession of 
the tail, and absence of all trace of keel or expansion on its upiier side. 
A young si)ecimen 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 length of 10 feet 3 inches. Common south of Cape Cod. 
Occasionally found northward. 
Dasibatis lata. 
(Garman, 1880, Ball. Mas. Comp. Zool. vi, p. 170.) 
Disk quadrangular, one-fourth wider than long. Anterior margins 
nearly straight, forming a very blunt angle at the snout, rounded near 
