the Morphology and Classification of the Saleniidte. 12 7 



the species {op. cit. p. 242). This description, made thirty- 

 one years ago, readily enabled the species to be distinguished 

 from all Acrosaleniai except A. Wiltoni, Wright, and A. La- 

 marcki) Desor. If the figure given by Desor (' Synopsis,' 

 pi. X. fig. 2) of ^. Lamarcki be compared with specimens of 

 A. Wiltoni, Wright, the distinction is evident. The shape 

 differs and the scrobicules of the great tubercles are separated 

 by two lines of granules ; the width of the median ambulacral 

 zone is less than that of ^. Wiltoni a,nd A. pustulata. The 

 small peristome and small ajjical system distinguish the foreign 

 species from A. inistulata. The distinction between A. pus- 

 tulataawA A. Wiltoni IS,, however, not great, and if the figures 

 given by Wright {op. cit. pi. xvi. figs. 2 a-f and 3 a-e) be 

 examined critically, the whole of the specific differentiations 

 rest upon the dimensions of the peristome. We cannot agree 

 to the correctness of Wright's fig. 2 d, pi. xvi., on which 

 much depends. The whole of the pairs of pores on the line 

 towards the interradium drawn are wrongly placed, and the 

 adoral pores are made aboral ; the arrangement of the tubercles 

 and the granules between them and in the interporiferous 

 area is not consistent with fact. There are really crowded 

 granules between the tubercles, and at least three vertical sets 

 of granules in the median area. 



The width of the ambulacra is, however, well shown in the 

 figure, and it is equal to that of a coronal plate bearing a large 

 interradial tubercle, that is, the breadth of one half of an 

 interradium. 



Thus the statement made by Wright that the ambulacra of 

 A. pustulata are narrow is contradicted. The truth is that 

 they are wide for the size of the test and not quite so wide as 

 they are drawn. 



Again, in fig. 2 <f, all the plates in tlie ambulacra are com- 

 pound ones ; and this is not correct, for the arrangement is 

 exactly like that of the species already noticed in this com- 

 munication. 



The relative size of the apical disk and the position of the 

 radials, and the number of accessory plates and the nature of 

 the dorso-central, depend largely on growth, the adults and 

 the half-grown differing considerably in these matters. 



The youngest specimen we have examined, which is suffi- 

 ciently well preserved to afford good results on examination, 

 is 18 millim. high and 9 broad. The apical disk is on tlio 

 whole tumid and raised above the test. The anterior basals 

 are larger than the postero-lateral ; basal 5 is well developed, 

 is about one third of the size of a postero-lateral, is angular 

 without and curved within, and has a single row of minute 



