ECHINOLAMPAS DEPRESSA. 339 



half an inch in length (PL XVI f. S- 10), the young Echinolampas resem- 

 bles Caratomus to such an extent that this stage was considered for a time a 

 living representative of Caratomus. The larger series collected by Mr. Pour- 

 tales, in his second expedition, showed conclusively the relationship to Echi- 

 nolampas, and proves the correctness of the step taken by Desor in removing 

 Caratomus and allied genera from the Galeritidae, and placing them among 

 the Cassidulidae, on account of the semipetaloid nature of the apical portion 

 of the ambulacra. Bifurcate pedicellariae with a short stem (PL XVI. f. 15) 

 and a large transparent head are irregularly scattered over the test ; the 

 spines resemble those of Clypeastroids (PL XVI. f. 16), 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 ; they are covered by dark pigment cells (PL XVI. f. IS) as long as the 

 specimens retain the aspect of Caratomus. The character of the tentacles 

 does not change in any part of the poriferous zone. They retain their disk 

 even after the petaloid nature of the abactinal part of the ambulacra is 

 fully developed and the pores are joined by a well-defined furrow; so that we 

 have the apparent anomaly of sea-urchins with petaloid ambulacra, yet pos- 

 sessing only tentacles differing in no way from those of the regular Echini. 

 A similar state of things has been shown to exist in the young of Echinan- 

 thus rosaceus at an age when the denuded petaloid ambulacra appeared to 

 differ in no wise from those of the adult, carrying well-developed lobed tenta- 

 cles in the petaloid portion of the ambulacra ; yet a young specimen, meas- 

 uring over an inch, was only provided with tentacles terminating in a 

 powerful sucking disk. 



The bare part of the posterior interambulacral area between the anus and 

 the actinostome, often so prominent in the adult, is not apparent in the young, 

 and is formed by minute miliary granulation, encroaching more and more 

 with increasing size upon the larger primary tubercles of the actinal surface. 

 There are no teeth nor signs of auricles in these young, so that we can as- 

 sume that the genera now associated with Cassidulidae, allied to the Carato- 

 mus and the like, were, as well as Echinoneus, edente. 



From 35 -160 fathoms. 



