210 D. Echinodennata. 



plechiuidae, 15 (0) Clypeastridae, 2 (1) Nucleolidae, 13 (12) Pourtalesiae, 6 (5) 

 Ananchytidae, 10 (0) Spatangina, 18 (10) Brissina. 



Die Diagnosen der 1 1 neuen Gattungen und der einen neuen Untergattung sind 

 folgende. 



Aspidodiadema gen. nov. Intermediate between the Cidaridae proper and the Dia- 

 dematidae. It has like the latter a thin test, with long hollow primary spines nearly 

 straight, and strongly vericillate, especially in the young. The miliary and se- 

 condary spines are like the primary radicles, only shorter and proportionally slen- 

 der. This genus has, like Centrostephanus, ten large plates on the buccal inein- 

 brane carrying miliary spines. The abactinal system is, as in the Cidaridae, large 

 and circular, but the genital and ocular plates are uniform in size, and form a 

 narrow ring as in Glyphocyphus round the membrane covering, as in the Dia- 

 dematidae, the large anal system. In the anibulacral system , as in Hemicidaris 

 and Salenia, two vertical rows of large tubercles limited to the ambitus and the 

 actinal system, and as in other Diadematidae the ambulacral system is broad com- 

 pared to that of the Cidaridae proper. The interambulacral system has, as in Ci- 

 daris proper, only two vertial rows of large primary tubercles. The test is glo- 

 bular, much as in Amblypneustes. The most remarkable feature of [this genus is 

 the structure of the ambulacral system ; the plates composing it are, as in the Ci- 

 daridae, small, arranged in two vertical rows, the plates are nearly of a size, and 

 each plate is perforated by a pair of large pores placed close together. The pores 

 are situated on the outside edge of the plates and run in a vertical line (not un- 

 dulating as in Cidaris) fi'om the apex to the actinal system. The primary tuber- 

 cles are perforated and crenulated. The teeth are grooved as in the Cidaridae 

 and Diadematidae. 



Micropyga, gen. nov. This genus, with its flattened test and short spines, is closely 

 allied to Astropyga, from which it mainly differs in the small size and the struc- 

 ture of the abactinal system, which resembles more that of Centrostephanus and 

 Aspidodiadema, and in the greater rigidity of the test as in Diadema ; the bare 

 sunken median interambulacral space, extending from the apical system towards the 

 ambitus, so characteristic of Astropyga, is narrow; it bears, as in Astropyga, small 

 primary tubercles, forming two vertical rows along the median ambulacral line. The 

 primary tubercles of the interambulacral areas above the ambitus are placed in the 

 centre of the plates, and arranged in one principal vertical row, with irregular 

 rows of smaller secondary tubercles. As in Astropyga the actinal floor is thickly 

 covered with large primary tubercles, deep actinal cuts are present, the poriferous 

 zone is narrow, the pores are in pairs arranged in two vertical rows, the spines 

 of the abactinal surface are short and slender like those of Astropyga proper, 

 while on the actinal side they are more or less club-shaped, or trumpet-shaped, 

 resembling somewhat the actinal spines of Astenosoma and Phormosoma, with 

 which both this genus and Astropyga have many points in common forming a con- 

 nection as it were between the Diadematidae proper and the Echinothuridae. The 

 primary and secondary tubercles are perforate, but not crenulate. The primary 

 and secondary ambulacral and interambulacral radioles are similar in structure, 

 with exceedingly fine verticillations, forming in older specimens a delicate longi- 

 tudinal striation. The long-headed pedicellariae closely resemble those of the Dia- 

 dematidae. 



Prionechinus gen. nov. The structure of the apical system of this genus is closely 

 allied to that of the Salmacidae. It resembles more, perhaps, that of the genus 

 Coptophyma of Peron and Gauthier ; but as in Cottaldia, there is but a single row 

 of plates of pores of equal size in the ambulacral zone. The actinostome is some- 

 what indented . and the actinal membrane is covered by plates. The spines are 



