REPORT ON THE ECHINOIDEA. 41 



The genus Schleinitzia was established by Studer (Proc. Berlin Acad., p. 463), 

 for a Cidaris in which the anal system is allied to that of Stephanocidaris, the 

 spines recalling Porocidaris, while the crenulation on which he principally based his 

 genus recalls Rhabdocidaris ; and it may possibly be that Studer 's Schleinitzia is 

 after all only a new species of Stephanocidaris or of Porocidaris, more prol^ably 

 of Stephanocidaris, since S. hispinosa, has crenulate tubercles, and pores joined by 

 furrows. 



Thomson (Trans. Eoy. Soc., 1874, vol. Ixiv., part 2, p. 726), in his description of 

 Porocidaris purpurata dredged in the " Porcupine " expedition, had already called atten- 

 tion to the simultaneous occurrence of crenulated and smooth tubercles on the same 

 specimen. He has figured these crenulated tubercles as existing in his specimen mainly 

 round the abactinal system (pi. Ixi. fig. 2). 



Until the publication of Thomson's paper, which seems to have escaped Studer, it was 

 supposed that the crenulation of the tubercles distinguished the fossil from the recent 

 species as a whole. The unsatisfactory nature of this character, however, was well known 

 from those groups among recent Echinids in which crenulated tubercles occur, and the 

 impossibility of assigning to it any definite value. In the Diadcmatidee and Pseudodia- 

 dematidse we find on the same specimens primary tubercles identical in size, which are 

 either crenulated or not. Loriol has expressed his oj^inion of the variability of this 

 character as regards fossil CidaridjB, of which the tests are frequently so admirably 

 preserved as to retain the smallest details of structure. Troschel, in 1877, called attention 

 to the presence of crenulated tubercles in a new species of Cidaris [Rhabdocidaris recens, 

 Archiv. f. Nat., vol. xliii. p. 127). Subsequently Troschel (Sitzungsb. d. Nieder Rhein 

 Gesell., Dec. 8, 1877) returns to the same species, caUing attention to the fact that Loriol, 

 on examining his specimens of Cidaris annidifera and Cidaris liltheni, found that in 

 both specimens the tests were covered with primary tubercles of which some were 

 crenulated and others smooth. Troschel at the same time shows that his Rhabdocidaris 

 recens is closely allied to Cidaris hispinosa. On the peculiar structure of the anal 

 system of Cidaris hisp>inosa, radically difierent from that of other Cidaridse, I had based 

 the genus Stephanocidaris (BuU. Mus. Comp. ZooL, vol. i.). I have also examined the 

 tests of Stephanocidatis hispinosa and of Phyllacanthus annxdifera in our collections 

 (Mus. Comp. Zool.), and find that in both these species we have existing on the same tests 

 tubercles more or less distinctly crenulated as well as smooth tubercles. In Stej^hano- 

 cidaris the crenulations were limited to those tubercles placed immediately round the 

 abactinal system, which, as is well known, are not the largest nor most characteristic 

 tubercles in the Cidaridae, and do not always carry spines identical in appearance with 

 the other primary spines of the test. In Phyllacanthus annidifera, on the contrary, the 

 crenulated tubercles were found irregularly scattered on the coronal plates. I may add 

 that I was much surprised to find on a specimen of Dorocidaris papillata (hystrix) 



(zOOL. CHALL. EXP. — PART IX. — 1881.) I 6 



