368 THE PLAGIOSTOMIA. 



have behind the head and farther back a series reaching the tail; others have 

 only small spines. The largest tubercles occur on the middle line of the tail in 

 front of the dorsals. The lower surface is smooth, except below the snout. 



Back uniform brown with or without a spot of lighter near each shoulder, 

 and another near the hinder angle of each pectoral. The lower surface is white 

 with the exception of an elongate spot of brown below the end of the snout. 



A fully developed male has a length of about 16 inches, or from snout to 

 pores 7i, from pores to end of tail 8|, and a greatest width of 8|. It has If rows 

 of teeth, ten of the outward rows with flat crowns like the female, the others 

 with a sharp cusp; the claspers are slender and long pointed and do not reach 

 to the first dorsal by more than twice the length of the dorsal base. From the 

 origin of the first dorsal to the end of the tail is 4^ inches; from the base of the 

 second dorsal to the end of the tail is 2? inches. The distance between the bases 

 of the dorsals is more than twice the base of the first dorsal. 



Rio Janeiro. 



Dactylobatus. 



Dactylobatus Bean & Weed, 1909, Proc. U. S. nat. mus., 36, p. 459. 



Disk subcircular, a few median rays of each pectoral produced beyond the 

 others, snout produced. Anterior nasal valves reaching the mouth, joined to a 

 wide isthmus. Ventrals deeply notched. Spiracles near the eyes, small. Tail 

 elongate, depressed, with a lateral fold on each side, with two dorsals near the 

 end and with a rudimentary caudal fin. Back roughened by spines and tubercles. 



Dactylobatus armatus. 



Dactylobatus armatus Bean & Weed, 1909, Proc. U. S. nat. mus., 36, p. 459, pi. 38. 



Disk rounded, broader backward, semicircular in front of a lateral process 

 from the middle of each pectoral and subquadrangular behind them; hinder 

 angles and margins rounded. Pectoral processes of about seven rays, blunt, 

 length about equal that of snout or width of mouth. Scattered spines on the 

 back, in two rows under the disk from below the pectoral extensions to near the 

 snout; larger tubercles occur in a row above each orbit, on each shoulder (one 

 or two) , and in a vertebral series from the head to the first dorsal. 



Ashy with spots of black, rounded to oblong in shape, small to large in size, 

 to some extent arranged in transverse series and in about a dozen transverse 

 bars between the back of the head and the first dorsal. 



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