482 AMBLYPNEUSTES PENTAGONUS. 



what has been called A. pallklus, but so slightly developed that it would 

 readily escape attention, and, owing to the different ground-color of the test, 

 — a yellowish or light violet, — the facies of this species is apparently quite 

 different at first; the coloring of the test is very uniform, and the brilliant 

 white tubercles stand out prominently upon the even background of the 

 test. The presence of secondaries and small miliaries in the narrow porif- 

 erous zone, as well as the less numerous median sutural pores, and the greater 

 uniformity of the tubercles and their more irregular arrangement, makes me 

 hesitate to separate these two species, which I am convinced will prove 

 identical, though the intermediate links are as yet wanting. The differences 

 I have pointed at above are the only ones by which 1 can distinguish them. 

 The scarcity of good series of Amblypneustes in our collections makes it diffi- 

 cult to give a satisfactory account of them ; and as they are extremely 

 variable in coloration, pattern, ornamentation, proportions of test, what I give 

 here concerning them must be taken only as a preliminary attempt to un- 

 ravel this difficull genus. 

 Australia; Feejee Islands. 



Amblypneustes pentagonus 



! AmUypneusles peutagonus A. Agass., 1872, Bull. M. C. Z., HL 



PI VIII .f. 7-8. 



Unlike the other species of Amblypneustes, the outline of the test from 

 above is pentagonal; the ambulacra projecting considerably beyond the con- 

 cave interambulacra. The coronal plates are high, not half as numerous 



as in other species of the genus of the same size. There is but a single 

 primary vertical row of tubercles both in the ambulacra] and in the interam- 

 bulacra! spaces, with remarkably well-defined and somewhat raised scrobicu- 

 lar circles, as in some species of Temnopleurus ; secondary tubercles few in 

 number, very irregularly scattered; sutural pores small, limited to the angle 

 of the plates; test thin, high, remarkable for the great size of the primary 

 spines. Abactinal system delicate, and not prominent and stout as in other 

 allied species. 



The abactinal system resembles somewhat that of Temnopleurus Reynaudi. 

 The madreporic genital is far greater than the other genital plates, which 

 are pointed, pentagonal, narrow ; three of the genital plates are separated 

 by large pointed ocular plates which reach the anal system ; the ocular 

 plates are notched at the outer extremity, with a deep narrow furrow near 

 the centre. 



