MUSEUM OF COMPARATIVE ZOOLOGY. 171 



papillaB. A row of small tubercles behind the head on the shoulder girdle. 

 It is likely that large specimens are provided with tubercles on back and tail. 



Distinguished from T. lata by the shape of the disk and snout, and the keel on 

 the tail ; from T. centrura by the straight margins of the pectorals and the keel. 



One specimen secured at Acapulco, Mexico, by Prof. Alex. Agassiz. One 

 light-colored, reddish-brown specimen from Panama, by the Hassler Expedi- 

 tion. 



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

 Length of body of second specimen 9.3, length of tail 24.5, and width of pecto- 

 rals 11.2 inches. 



Trygon brevis n. sp. 



Disk quadrangular, a little wider than long. Anterior margins nearly 

 straight, curved near the outer extremities to meet the convex posteriors, meet- 

 ing in a blunt angle on the end of the snout. Outer and posterior extremities 

 of pectorals round, without trace of angles. Ventrals broad, truncate, with 

 angles rounded. Tail less than one and a half times the length of the disk, 

 tapering to an acute point, depressed as far as to the spine, thence compressed 

 to the end of the cutaneous fold and round from this point to the end, with a 

 short elevated membranous expansion behind the spine, and a longer and wider 

 one on the lower side extending below the former and the spine. The expan- 

 sions have their hinder extremities opposed ; they end quite abruptly, and are 

 widest near the termination. Mouth with five papillse, outer small. Teeth 

 small, blunt. Upper jaw indented in the middle ; lower, with a prominence in 

 front. Disk naked in the young. Adult specimens have three rows of tuber- 

 cles on the middle of the back disposed as are those of T. hastata. A large 

 specimen from Payta has three large, erect, broad-based tubercles in front of 

 the caudal spine, and the tail rough with smaller ones. The short rows on the 

 shoulders contain from one to four, and probably increase in number with age, 

 as is the case with closely allied species from the Atlantic coast. 



Color olive or grayish brown, reddish near the edges ; below white, with 

 round spots of brownish under the base of the tail. 



Compared with hastata this species differs in the shorter tail, the rounder 

 extremities of the disk, and the shape and size of the tubercles and membra- 

 nous fins. 



T. hastata has no expansion on the top of the tail, and that on the lower side 

 is very long, of moderate width, and tapers gradually. Those of brevis are 

 comparatively short and broad ; they rise gradually and terminate abruptly. 



From T. Sayi this species is to be distinguished by the great development of 

 the caudal expansions, their shape and length, and by the tubercles on shoul- 

 ders and tail. A large female measured in length of body 17, length of tail 23, 

 and width of pectorals 18 inches ; a young male, length of body 8.1, length of 

 tail 12, width of pectorals 9.2 inches. 



Including this and the preceding, the number of American species properly 

 belonging to the genus Trygon is increased to seven. 



