REVIEW OF OPHIODERMA 191 



yellow, fading gradually to the arm tips and blending into the chocolate 

 brown of the upper arm. 



Six specimens from the Galapagos Islands differ in having a more 

 pentagonal disk and more delicate arms, with an average arm length of 

 2.8 times the disk diameter. The upper disk is a reddish-brown without 

 any markings or black-lined rings. The under side is a lighter reddish- 

 brown without markings and the arms are of the same color. The typical 

 robust chocolate brown phase with black-lined rings on disk and golden- 

 yellow under arms was also found in the Galapagos Islands. 



Three individuals taken at Port Utria, Colombia, are of the heavy 

 robust form with arms three times the disk diameter in length. The 

 upper disk is brown, uniformly speckled with a light tan, the specks 

 becoming larger distally and extending out on the upper arms to the tips. 

 The spots on the upper arm plates are in two transverse rows running 

 across the arm. Basally there are about 20 spots on the upper arm seg- 

 ment, reducing proportionately to about 12 distally except for the 

 extreme arm segments. The under disk and oral shields are speckled and 

 the mouth parts and under arms are yellow, the color blending distally 

 into the brown of the upper surface. The southernmost specimens from 

 La Plata, Ecuador, are typical in form and have the characteristic 

 chocolate brown disk with thin black-lined rings inclosing areas of 

 lighter brown on both the upper and under disk. The mouth parts and 

 basal arm plates have the golden-yellow coloring. 



The color of O. teres varies usually according to geographical loca- 

 tion and habitat, though several color phases have been taken at the same 

 location. Therefore the writer does not believe it is justifiable to dis- 

 tinguish each color phase as a variety or subspecies as H. L. Clark ( 1940, 

 p. 342) did for the large size adult, which is uniformly dark brown. 

 Adult dark brown specimens in the Hancock Collection have been taken 

 from the west coast of Baja California, Mexico; Gulf of California, 

 Mexico; and the Galapagos Islands. 



One may summarize the most distinctive characteristics of O. teres 



as; 



1. Fragmentation of the upper arm plates, becoming more pro- 

 nounced in the larger specimens. 



2. Higher, more pronounced rounded arms, especially in the larger 

 specimens, in contrast to the flat arms of O. panamense. 



3. The brown color, without arm banding, even in the youngest 

 specimens. 



