REPORT ON THE ECHINOIDEA. 147 



in profile, the test slopes regularly from the anterior to the posterior extremity in the 

 adult (PI. XXX. fig. 2), this posterior extremity is sharply arched over the anal hood 

 then vertically truncated, sloping anteriorly with a rounded corner joining the indistirict 

 actinal keel (PL XXIX. figs. 2-4). In younger specimens the anal system is more at 

 the extremity of the narrow end of the test (PI. XXX. figs. 5, 9, 13), and the actino- 

 stome is also somewhat more central (PI. XXX. figs. 3, 10) than in the older specimens 

 (PI. XXIX. fig. 3). In the youngest specimens, measuring 14 mm., there is already an 

 indistinct subanal fasciole (PI. XXX. fig. 19) ; this fasciole is never very distinct, the 

 miliaries of the band being always more or less disconnected as in the specimen figured 

 on Plate XXX. fig. 19, which measured 24 mm. in length. The anal system consists of 

 numerous small irregularly-shaped plates (PI. XXX. fig. 18). The indistinct actinal keel 

 of Urechinus is scarcely more prominent than in such genera as Rhynchopygus and 

 Cassidulus. Large trifid long-stemmed pedicellariae (PI. XXX. fig. 22) are found in 

 the actinal region near the actinostome ; the shorter round-headed pediceUarise 

 (PI. XXX. fig. 23) occur on the abactinal surface of the test above the ambitus. 



A large number of specimens of this species were collected, showing a great degree of 

 variation in the tuberculation of the abactinal surface of the test (compare Pis. XXX. 

 and XXX.''), in the outline of the test not only when seen from above (PL XXX. 

 figs. 1, 7), but especially when seen in profile and from the anterior and posterior 

 extremities (compare PL XXX. figs. 2, 5, 6, 9, 13, with PL XXX.» figs. 3, 4, 5, 7, 

 12-14). 



In the specimen figured on Plate XXX.'' figs. 7-9, we find that it agrees very closely 

 with the young of Plate XXX. figs. 1-3. In another specimen (PL XXX." figs. 10-14) 

 the outline in profile is quite difierent (PL XXX." fig. 12), the test is highest posteriorly, 

 and we find a slight tendency to the development of an anal snout. The anal system is 

 more elliptical (PL XXX.* fig. lOo), and the subanal fasciole is quite markedly developed, 

 and the primary tubercles are somewhat more numerous. This specimen also had only 

 three genital pores, whUe in specimens of the size of fig. 8, Plate XXX." there are usually 

 four. The madreporic body is quite indistinct both in figs. 8 and 11 (see fig. 8a). There 

 is in these two specimens (PL XXX." figs. 9, 10) quite a marked accumulation of mUiaries 

 on the edge of the actinal interambulacral plate, rudimentary bourrelets as it were. 



I have also figured on Plate XXX.* figs. 1-6, an elongate conical specimen of 

 Urechinus, which I refer with some doubt to this species. At first sight it appears 

 totally distinct, but with the exception of the apex of the test there are no structural 

 difi"erences to be noticed in this specimen. The test is comparatively thitiner ; the 

 striking feature is the great development of the anterior lateral interambulacra near the 

 apical part of the test, forcing the ambulacra towards the posterior extremity (PL XXX.* 

 figs. 1, 3). It is difficult to make out satisfactorily the plates composing the sharp crest 

 which forms the apex of this specimen (PL XXX.* figs. 1, 3, 4, 5). We could imagine 



