Prof. P. M. Duncan on the Salenidae. 249 



Tertiary form there are as many as fifteen primary tubercles 

 in an interambulacrum. But, on the other hand, it is evident 

 that the number of primary tubercles is indicated long before 

 the test assumes its largest size. 



The recent Salenida? now under examination have all two 

 rows of small secondary tubercles in each median interradial 

 space ; and in this they differ remarkably from the Australian 

 Tertiary Salenia, but resemble the Xummulitic species. 



A row of small secondaries is placed just outside the pori- 

 ferous zone in Salenia profundi. The ambulacral tubercles 

 of Salenia profundi are very decidedly smaller than the largest 

 of those of the interambulacra ; they are small, numerous, in 

 two vertical rows ; and two or three near the peristome are 

 slightly larger than the others. They are placed so that there 

 is a free vertical space between the rows, in which are placed 

 the vertical set of pedicellari^. Omitting the remarks about 

 the pedicellariffi and the larger tubercles, the same arrange- 

 ment prevails in the other Salenidae as yet knoAvn from the 

 deep sea. The ambulacra are narrower than the interambu- 

 lacra in all, and they slightly diminish in breadth at the peri- 

 stome. 



As the test of the specimen of Salenia profundi is not 

 denuded, it is impossible to estimate the number of the pores 

 in the poriferous zone ; but the presence of some tentacles 

 close to the peristomial end of the ambulacra indicates that the 

 pores are in simple series and comparatively few in number. 

 In this the species conforms to the description of the vai'ispine 

 form by A. Agassiz, and also to that of Salenia Goesiana, 

 There would apjjear to be a single pair of pores to each ambu- 

 lacral plate ; and, as far as I can determine, each plate has an 

 ambulacral tubercle parallel with the pores. This is not what 

 ofcurs in the Tertiary forms or in those of more ancient date ; 

 for in them there is a pair of pores in relation with each 

 ambulacral tubercle, and also a pair intermediate and in 

 relation with a space between the successive vertically ar- 

 ranged tubercles. The tentacles of Salenia profundi are stout, 

 not very long, and jjresent a stem and disk. The stem is 

 constricted here and there transversely ; and the circular disk 

 is occasionally ragged at the margin or is marked there by 

 slight furrows. The base of the tentacle is often pigmented. 

 Loven states that in Salenia Goesiana the pores are in simple 

 series and are surrounded by an oval " enceinte " with raised 

 edges. This is not ap])arent in the other recent Salenida?, 

 but it is not without its analogue in some fossil forms. 



A. Agassiz was struck with the varied nature of the spines 

 of the form he describcil from the Florida Expedition ; and 



