190 ZIESENHENNE 



Galapagos Islands, and the Gulf of California. Common. 77 

 specimens in Hancock Collection. 



As early as 1889 Ives noticed the variation in color and characteristics 

 of O. teres and O. panatnense. Nielsen (1932, pp. 328-330) and Clark 

 (1940, p. 342) have also discussed the relative merits of the distinguish- 

 ing characteristics of O. teres. 



In the Hancock Collection there are 77 specimens collected from 

 the west coast of Baja California, Mexico, the Gulf of CaHfornia south 

 to Ecuador, and the Galapagos Islands. Lyman's description v^^as of an 

 adult from Panama with a disk diameter of 32 mm and an arm length 

 of 133 mm, and listed four outstanding characters: broken upper arm 

 plates, concealed radial shields, proportionately shorter arms, and purple- 

 brown color without mention of banding. Nielsen (1932, p. 333) added: 

 "A more reliable character are [Wc] the roundish arms of O. teres, those 

 of O. panatnense being more flattened." Only 15 of our largest specimens 

 agree with the above five characteristics and thus could be classed as 

 typical O. teres. 



The largest specimens were taken at the extreme northern range, 

 from a reef located 10 miles west of Malarrimo Point, west coast of Baja 

 California, Mexico. The series ranges in size from 25 to 42.5 mm in 

 disk diameter and 91 to 162 mm in arm length. The radial shields in 

 this lot are concealed by granules, while the largest specimen from the 

 Galapagos Islands (disk diameter 37 mm, arm length 143 mm) has 

 exposed radial shields and five sets of pore pairs. Another series of fifteen 

 specimens from Guaymas Bay, Sonora, Mexico, have concealed radial 

 shields. They range in size from 17 to 35 mm in disk diameter and 51 

 to 136 mm in arm length. These specimens have the upper arm plates 

 divided into four or five plates basally and two to three distally. The arms 

 are strongly rounded and the color is a uniform brown on the upper 

 surfaces and a lighter brown on the under side. 



The smallest specimens were collected at Espiritu Santo Island in the 

 Gulf of California and have a disk diameter of 10 mm and an arm length 

 of 21 mm. In general the smaller specimens have exposed radial shields 

 and fewer divisions of the upper arm plates. The color is a rich chocolate 

 brown on the upper surface with thin black-lined irregular rings on the 

 disk; within the rings the color is a lighter brown. There is definitely 

 no banding of the arms. The color pattern of the upper disk continues 

 on the under interbrachial areas. The mouth parts and the oral shields 

 are lighter brown, the under arms within the disk diameter rich golden- 



