290 HAWAIIAN AND OTHER PACIFIC ECHINI. 



about .40 mm. in length. The ophicephalous are common but small; the valves 

 are only .20-.25 mm. besides the loop, and are very slightly constricted at the 

 base of the blade. The tridentate seem to be rare and the only ones found were 

 on the abactinal surface. The valves (PI. 93, fig. 23) measure about .55 mm. 

 in length and resemble those of Nudechinus darnleyensis as figured by Mortensen 

 but are somewhat flatter and more compressed at base of blade. 



The test is dull gray with a purplish cast which becomes deeper on the abacti- 

 nal median areas of both ambulacra and interambulacra, which thus stand out 

 more or less clearly as darker regions; actinally the whole test is nearly white. 

 The spines are light, particularly the secondaries. The primaries are violet or 

 pale reddish with a broad indistinct violet band, and with the tip light. The 

 general appearance of the preserved specimens is very dull. 



The specimen selected as the type of this species was collected by Semper at 

 Bohol, Philippine Islands, in 6-10 fathoms of water. It came into the M. C. Z. 

 collection in 1873 but was never identified. There are also two other specimens, 

 which bear the label "Echinus darnleyanus Wood. Australia," but there is no 

 clue as to when they were received or whence they came. The label would 

 seem to confirm Mortensen's view that Wood confused more than one species 

 under his Echinus darnleyensis, for these specimens are certainly very different 

 from those in the British Museum which bear that name. 



TEMNOPLEURID^E Desor. 

 GENERAL CONSIDERATIONS. 



The description of the Temnopleuridse as Echinidae with sculptured or pitted 

 tests expresses briefly the only difference between the two families. It is difficult 

 to determine just what the real importance of this character is, and the recogni- 

 tion of the Temnopleuridae as a separate family is merely a matter of convenience. 

 Where the sculpturing of the test is conspicuous or the pits are deep and large, 

 the general appearance of the animal seems to warrant the separation from the 

 Echinidae, but where the sculpturing is very faint as in many specimens of 

 Prionechinus, or the pits and grooves are so small or shallow as to be seen only 

 with difficulty as in some specimens of Salmacis (and other genera), the line 

 between the families is virtually blotted out and one can but wonder whether 

 it really exists. It is not strange therefore that specimens of Echinidse have 

 often been identified as Salmacis, and specimens of Genocidaris and related 



