292 HAWAIIAN AND OTHER PACIFIC ECHINI. 



importance, but since it is only the recent species of which the entire structure 

 and the complete life-history can be discovered they should, when possible, 

 furnish the types upon which names are based. It is to be regretted that the 

 number of fossil Temnopleuridse, which have been named, is so large as to make 

 it impossible to take them into account in the present work, and the following 

 review of the recent species of the family is given with the full understanding 

 that a similar review of the fossil forms may make it necessary to modify some 

 of the statements and to alter the generic limits herein laid down. 



In no other family of Echini is there more general agreement as to the classifi- 

 cation of the recent species than is found here, no doubt owing to the fact that 

 all students of the group have sought for generic characters in the test and have 

 made use of the spines and pedicellariae only in a very subordinate way. The 

 family contains at least fifty living species and probably many more, for specific 

 limits in some genera are as yet unsatisfactorily known, and moreover the 

 smallest species of regular Echini belong here and these are often overlooked by 

 collectors. Even if collected, their identification being difficult, they are often 

 erroneously labelled, frequently being considered the young of large species to 

 which they have no close relationship. It is therefore to be expected that more 

 species will be added hereafter to the Temnopleuridse than to any other family. 



As stated above the family falls into two sections according to the structure 

 of the test. In one group (Trigonocidarinse) the coronal plates, especially in 

 the interambulacra and abactinally, are more or less sculptured, i. e. the surface 

 of the plate is furrowed or is ornamented with elevated ridges or knobs or both. 

 The amount of this sculpturing is very variable even within a given species, 

 some specimens showing it plainly while in others it is very faint. Thus we have 

 specimens from the West Indies, which connect Trigonocidaris albida with 

 Lytechinus euerces so closely that it is to be feared the line drawn in this Memoir 

 is quite arbitrary. Specimens showing any "sculpturing," have been assigned 

 to Trigonocidaris and those where it was lacking to Lytechinus, but many of the 

 latter have a most close resemblance to the former. It may be added that most 

 of these doubtful cases are immature, though occasionally a full grown Trigono- 

 cidaris has the " sculpturing " very faint. In Prionechinus again, the amount 

 of sculpturing is oftentimes very slight, no more than is found in young 

 Echinidse of the same age, and the placing of such specimens in the Temno- 

 pleuridse is on the strength of their general appearance rather than on anything 

 tangible. Sometimes the abactinal system is sculptured even when the test is 

 not but this is not usually the case. In the other group (Temnopleurinae) the 



