﻿FROM THE LOWER GREEN SAND. 



247 



Clypeopygus Fittoni, Wright, nov. sp. PI. LVI, fig. 1 — 3. 



Test oblong, upper surface depressed, highest posteriorly ; under surface concave ; 

 ambulacra narrow, lanceolate ; poriferous zones subpetaloidal above and narrowly biserial 

 on the sides and base ; apical disc nearly central ; vent-opening at the end of a narrow 

 sinus with vertical walls ; mouth-opening at the junction of the anterior with the middle 

 third, peristome surrounded by five prominent lobes and five pairs of subpetaloidal 

 pores, forming together a well-marked rosette. 



Dimensions. — No. 1, length ly^- inches, breadth 1 inch; No. 2, length 1^ inches, 

 breadth inch. 



Description. — The outline of the test is oblong, with the sides slightly compressed ; 

 the upper surface is convex, flattened at the anterior half, and gradually elevated towards 

 the posterior third, which is the highest part of the test (PI. LVI, fig. 1 d, fig. 3 e) ; from 

 this point it bends abruptly down to the posterior border; Mr. Bones' capital figures 

 in PI. LVI make this character of the test far more intelligible than the most laboured 

 description could effect. 



The ambulacral areas are narrowly lanceolate, the antero- and postero-lateral pairs 

 are long and flexuous, and the single area is short and straight ; the poriferous zones 

 (fig. 3 /) are slightly subpetaloidal on the dorsal surface (fig. 1 b, fig. 3 b), and closely 

 biserial on the sides and at the base (fig. 1 d, e, fig. 1 c, fig. 3 c) ; as they approach the 

 peristome, they expand and form five petaloidal expansions around the mouth, which are 

 separated from each other by the five lobes that surround the oral opening (fig. 3 c). 



The inter-ambulacral areas are largely developed ; the antero-lateral are the narrowest, 

 the postero-lateral the widest, and the single area of intermediate width ; they are built of 

 large plates bent in the middle, having their surface closely covered with small scrobicu- 

 lated tubercles arranged in horizontal rows ; fig. 1 / shows three of these plates and a 

 corresponding portion of the ambulacral area with the poriferous zones, magnified six 

 diameters. The tubercles at the base are larger and wider apart than those on the 

 upper surface, as shown in fig. 3 g, where a portion of the base is magnified three 

 diameters ; the boss, area, and imperforate tubercle are well seen in this drawing. 



The vent opens at the end of a deep sulcus near the middle of the dorsal portion of 

 the single inter-ambulacrum: see figs. 1 b, e, fig. 3 b,d; the walls of the sulcus are 

 abruptly perpendicular (fig. 3 b, d, e), and the oval periprocteis seen at the upper portion 

 thereof (fig. 1 e, fig. 3 b, d) ; the single inter-ambulacrum exceeds in height all the others, 

 for its upper surface is elevated (fig. 1 a), and forms the vertex of the test, whilst its 

 under surface is curved downwards and forms a marked prominence in the base 

 (fig. 1 d, e, fig. 3 a, e) : I have not seen the apical disc well shown in any specimens. 



