REVIEW OF OPHIODERMA 193 



Ophiodcrma panarnense H. L. Clark, 1910, Bull. Mus. Compar. Zool., 

 vol. 52, p. 340, pi. 8, fig. 2. 



Ophiocryptus granulosus Nielsen, 1932, Vidensk. Medd. Dansk Natur- 

 hist. Foren., vol. 91, p. 334, fig. 38. 



Littoral to 10 fathoms. San Pedro, California, south to Payta, 

 Peru ; Galapagos Islands, Cocos Island, Guadalupe Island, So- 

 corro Island, Clarion Island and the Gulf of California. Very 

 common. 2389 specimens in the Hancock Collection. 



In 1940 a series of 284 specimens of Ophioderma panarnense ranging 

 in disk diameter from 2.3 to 21 mm and in arm length from 6 to 77 mm 

 was collected on a rocky reef at low tide at Puerto Refugio, Angel de la 

 Guarda Island, Gulf of California, Mexico. In this series, 96 specimens 

 have a disk diameter of 6 mm or less, 30 have 7 mm, and many more have 

 less than 9 mm. A study of the development of the growth of O. pana- 

 rnense as illustrated by this series follows. 



Specimens with a disk diameter of less than 3 mm are entirely cov- 

 ered with granules except for the outer third of the under arm plates. 

 The length of arms averages 2.3 times the disk diameter, and only four 

 arm-spines are developed at this stage. 



Specimens with a disk diameter between 3 and 3.5 mm show less 

 granulation. The granules are lost on the center of the upper and under 

 arm plates, except for the four basal segments. The side arm plates, disk, 

 and mouth parts are concealed by granules and five arm-spines are 

 developed. 



Specimens with disk diameters between 3.5 and 4 mm have still fewer 

 granules present. A few distal arm segments, side arm plates, four basal 

 arm segments, and the disk are covered by granules, and there are fewer 

 granules on the mouth parts. The arm length varies from 2 to 2.5 times 

 the disk diameter. The arm-spines are still five in number. The color 

 banding on the arms becomes very distinct at this stage. 



At the 4 mm disk diameter stage, the granules are disappearing from 

 the side arm plates, the madreporite becomes prominent and exposed, and 

 a few scattered granules remain on the basal under arm plates. The upper 

 arm plates are practically free of granules. The arms are now 2.5 to 3 

 times the disk diameter in length. The arm-spines are still five in number 

 but have grown considerably longer. 



At the 5 mm disk diameter stage, the oral shields are exposed. The 

 upper and under arm plates are free of granules and only the four basal 

 side arm plates bear granules. The mouth parts still retain much of the 



