MUSEUM OF COMPARATIVE ZOOLOGY. 298 



mouth opening in the centre. There are as yet no signs of phyllodes 

 or of bourrelets, which appear only later, the bourrelets being at first 

 accumulations of small tubercles between the phyllodes. When 

 measuring about half an inch in length, the young Echinolampas re- 

 sembles Caratomus to such an extent that this stage was considered 

 for a time a living representative of Caratomus. The larger series col- 

 lected by Mr. Pourtales, in his second expedition, showed conclusively 

 the relationship to Echinolampas, and proves the correctness of the 

 step taken by Desor in removing Caratomus and allied genera from 

 the Galeritidaj, and placing them among the Cassidulida\ on account of 

 the semipetaloid nature of the apical portion of the ambulacra. Pedi- 

 cellaria 1 with a short stem are irregularly scattered over the test ; the 

 spines resemble those of Clypeastroids, being short, slender, straight, the 

 secondary spines silk-like. The tentacles, as far as could be ascertained 

 from alcoholic specimens, are provided with a powerful sucking disk, as 

 long as they retain the aspect of Caratomus. 



Among Spatangoids proper, the examination of young specimens 

 shows that they undergo great changes in outline during their growth, 

 that the posterior part of the test is especially subject to variation, that 

 the position of the anus is exceedingly variable in one and the same 

 species, that the mouth is not labiate in the young as in the adult, that 

 the peripetalous fascioles and lateral fascioles do not change in their 

 limits, but that the subanal and anal fascioles are liable to great modifi- 

 cations during their growth, and cannot be used as distinguishing features 

 of generic value, while the permanence of the peripetalous and lateral 

 fascioles is of great systematic value. The ambulacral petaloids also are 

 greatly modified with age, generally becoming confluent, while in the 

 young they are remarkably distinct and the pores not conjugated. The 

 semitre are not covered by regular pedicellarhv, as is universally stated 

 to be the case. We find on the fascioles minute tubercles carrying 

 embryonic spines. Trosc'.iel was the first to call attention to this, and 

 Muller has subsequently, in his Embryology of the Echinoderms, given 

 accurate figures of the spines of the fascioles of S. canaliferus, in Ids 

 sixth Memoir, Plate VII. figs. 7-9. Yet these observations, dating 

 back to 1852, seem to have escaped the attention of recent writers, who 

 persist in stating that the fascioles carry true pedicellariae. These are 

 found irregularly scattered over the test, generally more abundantly 

 round the mouth. From the examination of the pedicellariae made in 



