MUSEUM OF COMPARATIVE ZOOLOGY. 291 



young Stolonoclypus prostratus, measuring half an inch in length, rec- 

 ognized a similar arrangement in the ambulacral zone, below the rosette. 

 It was now plain that our Florida Echinocyamus was only a young 

 Stolonoclypus prostratus, which in the earlier stages is identical in every 

 structural feature with Echinocyamus; for European specimens of 

 Echinocyamus show the presence of similar horizontal rows of pores, as 

 in our young Stolonoclypus from Florida. I am well aware that no Cly- 

 peaster has been found in European seas, yet we have evidently such 

 an incomplete knowledge of the marine Fauna, existing at great depths, 

 to judge from the collections made by Mr. Pourtales, that negative 

 evidence can no longer be admitted in opposition to such positive proof 

 as we find in Florida. The larvae referred by Miiller to Echinocyamus 

 were net raised by artificial fecundation ; they do not resemble Spatan- 

 goid or Clypeastroid larvae, but seem closely allied to true Echinidae 

 larvae. Can they not be larvae of Cidaris hystrix and of Cidaris papil- 

 lata — which would account for the presence of such forms in the North 

 Sea and Mediterranean — rather than be referred to Echinocyamus ? 

 Very small specimens varied in the number of the tubercles on each 

 plate, the number of pores of the imperfect rosette, the changes being 

 similar in kind to those observed in the Scutellidae. From the Echi- 

 nocyamus stage they become more pentagonal ; the concavity of the 

 lower side increases, the partitions increase by the addition of needle- 

 shaped processes, and they soon attain the shape and structure given 

 by Liitken in his figures of young Stolonoclypus prostratus. The 

 tubercles increase more rapidly near the edge of the test, and a re- 

 markable feature of these stages is the presence of minute glassy 

 tubercles similar to those of Echinoneus, developing side by side with 

 young tubercles, the function of which is as obscure as it is in Echi- 

 noneus. and which are not found in older specimens. 



The development of Echinolampas has thrown unexpected light 

 upon the affinities of the toothless Galerites and of the Cassidulida-. It 

 shows conclusively that Echinoneus is only a permanent embryonic 

 stage of Echinolampas, thus becoming allied to the Cassidulida^, and that 

 it has nothing in common with the Galerites as I would limit them, 

 confining them entirely to the group provided with teeth. This re- 

 duces the type to a most natural division, and from what we now know 

 of the simple nature of the ambulacra of all Echini in their early stages, 

 I would not give to this feature the significance which it has received, 



