44 



to the pedicellariæ the most distinct chnracter is found in llie triphylloiis ones; 

 they remind one very miuii of those of the Echinothnrids, the blade being closed by 

 a large cover])late in the lower ])art and the outer edge being serrate. The ophi- 

 cephalous pedicellariæ occur in two dilVerenl forms, a small form with or without 

 glands on the stalk, and a large form without glands on the stalk. (To be sure the 

 large form has not been found in all the species, but as its occurence in the species, 

 where it is known, is rather variable, it is allowable to supj)ose, that it will be 

 found on further examination of more material in all the species). The characters 

 here pointed out are certainly very slight, but added to the characters found in the 

 test they can only strengthen the view that these two genera form a separate family 

 of Diadematids. Gregory unites Aspidodiadema with the genera placed by Duncan 

 in the subfam. Orthopsinœ and makes thereof a family Orthopsidœ. I cannot agree 

 with Gregory herein. Aspidodiadema and Plesiodiadema have perforate and crenu- 

 late tubercles, but among the genera of „Orthopsinœ'' this is the case only in Eodia- 

 dema. This genus (according to the description) must certainly be very nearly 

 related to Aspidodiadema: but none of the other genera ])laced here by Gregory 

 have perforate and crenulate tubercles, and I can accordingly see no ])roof that they 

 are nearly related to Aspidodiadema. We must then retain the name Aspidodiadema- 

 tidœ for this family, as well because of its priority as because it is very doubtful, if 

 the genus Orthopsis does really belong to this family. 



The separation of the genus Micropyga from the fam. Diadematidœ is cer- 

 tainly correct. In addition to the characteristic arrangement of the pores in sets of 

 two it dilfers from all other Diadematids by its peculiar anchorshaped spicules. 

 (Bell in his Note on the Spicules of the Regular Echinids >) has already expressed 

 some doubt, if Micropyga has been rightly united with the Diadematids, on account 

 of these spicules). On the other hand I must doubt the correctness of referring it to 

 the subfamily Diplopodinœ, nay even the correctness of making a family or subfam. 

 Diplopodince at all. It is a very obvious character, to be sure, the arrangement of 

 the pores in sets of two; but it is also certain, I think, that all the forms with the 

 pores arranged in this way are not really nearly related. It may well be supposed 

 that the biserial arrangement has originated independently in différent families, as is 

 certainly the case with the polyporous arrangement. If we look to the orna- 

 mentation of the tubercles in the genera referred to the Diplopodidw, we lind that 

 Diplopodia and Pedinopsis have perforate and crenulate tubercles, Aca;i//iec/!i/iH,s and 

 Asteropsis imperforate, crenulate, and Phymecliiinis, Uiplotagma and Plistophyma 

 imperforate, noncrenulate tubercles. Finally Micropyga alone has perforate noncre- 

 nulate tubercles. This „family" accordingly seems very unnatural. It ought also 

 to be remembered that in Pttymosonia the pores are biserial on the abactinal side; 

 but even Duncan has not ventured to be consistent and transfer this genus to the 



') Journ. R. microsc. Soc. 2. Ser. II. 1882. p. 298. 



