336 ECHINOLAMPAS DEPRESSA. 



What was striking in these fragments was the distinct continuation of the 

 poriferous zone beyond the ambulacra! rosette and beyond the ambitus, a fea- 

 ture which would at once distinguish it from either Echinolampas Hellei or 

 E. oviformis. In the second expedition he dredged from a depth of thirty- 

 five fathoms off the Tortugas a small specimen measuring over an inch in 

 length (PL XVI. f. 17- 19). The general outline resembles strikingly that 

 of E. Hellei; it is, however, much more depressed, and differs by the peculiar 

 structure of the ambulacral rosette ( PL XVI. f. Si). Both in the posterior 

 and anterior pairs of ambulacra the rosette is not strictly petaloid ; the outer 

 poriferous zones of each of the lateral ambulacra are very irregularly devel- 

 oped. In the posterior pair the anterior poriferous zone (the part forming 

 the rosette) is fully developed to about the point where the rosette usually 

 terminates in the other species of Echinolampadae, while in the inner or pos- 

 terior poriferous zone the portion where the pores are joined by a groove is 

 not quite half as long as the adjoining poriferous zone. In the anterior late- 

 ral pair, the posterior poriferous zone is the short one, and in the odd ante- 

 rior ambulacrum it is either the left or the right poriferous zone which is 

 the shortest. This same structure also occurs in several fossil species. 

 Unlike the other species of Echinolampas, the outer poriferous zone extends 

 unbroken to the mouth; the two rows of pores are not placed (dose together; 

 it is always the exterior row of pores which is continued from each zone, and 

 not pairs of pores, as is uniformly represented in all drawings of fossil Echi- 

 nolampadae. The ambulacral zone also widens between the poriferous zone, 

 as it approaches the ambitus, and as the poriferous zone is sunken and the 

 ambulacral slightly raised, the ambulacra have very much the appearance 

 of the ambulacral zones of Echinoneus. Round the mouth the pores form 

 a very distinct floscelle. What is remarkable in this young Echinolampas 

 is the absence of the peculiar bourrelet (PL XVI. f. 20) so characteristic 

 of the other genera of Echinolampadae, the only sign we have at present 

 of them being an accumulation of small tubercles closely crowded to- 

 gether, which occupy the interambulacral spaces, and are identical in 

 arrangement with those found on the bourrelet of older Echinolampadae. 

 The peculiar bare space of the actinal interambulacral space so charac- 

 teristic of some fossil species of Pygorhynchus, is well marked, though in 

 older specimens of Echinolampadae this band nearly disappears, there 

 being but very faint traces of it left. The primary tubercles are by far 

 less numerous in this species than in either the E. Hellei or E. oviformis ; 



