434 PROF. F. J. BELL ON A NEW SPECIES OF MESPILIA. [Mar. 15, 



special point which characterizes this new species will perhaps bring 

 into prominence the whole question of the real affinities of these 

 forms: it is the well-marked character of the gili-cuts of the acti- 

 nostome, which, in the only species of the genus known hitherto, are 

 so very feebly developed. 



The specimen on which the following description is based was 

 presented by the Rev. S. J. Whitmee, and is stated to have come from 

 the Samoa Islands. It is in the dry condition. The test, from 

 above, is obscurely pentagonal in form, and not at all high ; the 

 spines are delicate, yellowish or greenish yellow in ground-colour, 

 and banded or tipped with red ; they are richly developed over the 

 whole surface of the test, with the exception of the middle portion 

 of the interambulacral areas. In correspondence with this there is, 

 of course, a portion of the interambulacral plates devoid of primary- 

 tubercles ; but this is only seen above the ambitus ; this bare band 

 is much narrower than in M. glolulus. At the ambitus there are 

 four large j^rimary tubercles in a row on either side of the middle 

 line ; the space on either side of these is occupied by smaller 

 tubercles, which are not quite so regularly arranged ; as we pass 

 nearer the actinostome, first these latter tubercles and then the 

 outer primary tubercles disappear ; those that remain retain or even 

 exceed the size of those at the ambitus. 



In the ambulacra! arese a row of four tubercles on either side 

 can likewise be made out at the ambitus. In having the same 

 number of primary tubercles in the interambulacral as in the ambu- 

 lacral area this species differs from M. glohulus, which, however, it 

 resembles in having the largest and most conspicuous of the inter- 

 ambulacral tubercles nearest to the poriferous zone. There is but a 

 very feebly developed, bare, intraambulacral space ; but the sutural 

 pores between the plates are more conspicuous in the ambulacral 

 than in the interambulacral arese. 



The gill-cuts are well marked and wide. The auricular foramen 

 is large, much larger than in M. glohulus, and quite as large as, if 

 not larger than, that of Amhlyjmeustes pallidus. The connecting 

 ridge is low, and, at its middle point, is produced into a short, 

 pointed, upwardly-directed process ; the actinostome is moderately 

 large. 



The abactinal area is by no means small ; all the oculars remain 

 shut out from the edge of the anal area ; and in no essential point 

 does it differ in character from that of M. globulus ; there is a rich 

 supply of tubercles ; and the peripheral anal plates are large and 

 tuberculated. The poriferous zone is not so wide as in M. globulus ; 

 but the pairs of por^s are still arranged in two vertical rows, and 

 the number of those in the outer seems to be about double those in 

 the inner row. 



The foramen of the pyramid is perhaps a little larger than in 

 M. globulus ; as in it, the radius is not bifid at its free end ; but its 

 spatulate character is very much more developed. 



The general ground-colour of the test is greyish brown ; the 

 tubercles are yellowish or whitisii. 



