REVIEW OF OPHIODERMA 197 



to a dirty white and very conspicuous. The under disk is cream, yellow, 

 or brown proximally, becoming darker distally and blending into the 

 olive green of the upper disk. The oral shields and under arms are light 

 olive green, with inconspicuous arm bands. 



Of the 2389 specimens of O. panamense studied, the most consistent 

 character is the banding of the arms, which is present even in the smallest 

 specimen with a disk diameter of only 2.3 mm. In contrast, no specimens 

 of O. teres have banding on the arms. For distinguishing these two species 

 the literature gives as characteristics of O. teres its relatively short arms, 

 its 9 arm-spines as against 1 1 for O. panamense, its covered radial shield, 

 and the division of the upper arm plates into three to five plates. Only 

 the last character is reliable, though some O. panamense display frag- 

 mented upper arm plates which are apparently the result of mechanical 

 damage. 



The Hancock material shows that the colorful coral-dwelling O. 

 panamense has relatively short and heavy arms, supposed to be a char- 

 acteristic of O. teres. Some large specimens of O. teres have the radial 

 shields exposed, while others of equal size have them concealed ; the 

 common green white-banded Gulf of California phase of O. panamense 

 has the radial shields concealed in the majority of specimens. So the 

 exposed radial shield as a characteristic of O. panamense is of little value. 

 Finally, the largest specimens of O. teres have 13 arm-spines and the 

 largest O. panamense have 12, proving that number of arm-spines is an 

 unreliable character. 



11. Ophioderma rubicundum 



O phioderma rubicunda Liitken, 1856, Vidensk. Medd. Dansk Naturhist. 

 Foren., p. 8; 1859, Norske Vidensk. Selsk. Skr., ser. 5, vol. 5, 

 p. 192, pi. 1, figs. 2a-2c. 



Littoral to 9 fathoms. Bahamas, Florida, and Dutch West Indies. 

 Not common. 



12. Ophioderma pentacanthum 



Ophioderma pentacantha H. L. Clark, 1917, Bull. Mus. Compar. Zool., 

 vol. 61, pp. 443-444, pi. 3, pi. 4, figs. 1-2. 



25 to 100 fathoms. Galapagos Islands and Gulf of California, 

 Rare. One specimen from the Gulf of California in the Hancock 

 Collection. 



