348 ECHINOBRISSUS 



5, 6). Nucleolites scutata, Lamarck, * An. s. Vert./ iii, p. 35; Defrance, 'Diet. Sc. Nat./ 

 vol. XXXV, p. 213. N. scutatus, Agassiz, 'Echin. Suiss.,' p. 45, pi. 7, figs. 19 — 21." This 

 quotation shows my lamented friend's opinion when the description of his PI. IX was 

 written. At that time I beheve he had not seen my Trouville specimens of E. scutatus, 

 for on making with him a comparison of some type-forms of N. scutatus, Lamk., he readily 

 admitted, after that examination, the specific differences existing between the N. clunicularis 

 and the true Lamarckian species. 



In my first memoir on the CassiduHdae of the Oolites,* I grouped several individuals of 

 this species with JE. dimidiatus, Phil. At that time nearly all the English Coral Rag 

 nucleolites were referred to PhilHps's species ; and I was only convinced of my error after 

 I had examined a series of good type-specimens from Trouville, the original locality 

 of Lamarck's species. 



Uchinobrissus scutatus, Lamk., when fully developed, is uniformly convex on the upper 

 surface ; it is rather narrower before than behind ; its length nearly equals its breadth, 

 when measured about the middle of the test ; the flanks are rounded and tumid (fig. 2 c), 

 and the posterior border is truncated (fig. 2 b) ; the vertex is situated nearer the anterior 

 than the posterior border, and in the centre thereof is placed the apical disc ; from this 

 point the test slopes gently towards the posterior border, but more abruptly to the anterior 

 side (fig. 2 c) ; the ambulacral areas are narrow, and nearly uniform in width, the 

 posterior pair being a little broader than the anterior areas. The poriferous zones are 

 petaloidal only on two thirds of the upper surface (fig. 2 a, c). The pores of the inner 

 row are round, those of the outer row form oblique slits ; on the flanks they are both round, 

 more distant, and placed obliquely, thus •.•..-,•; at the border they become very small, 

 and at the base indistinct; near the peristome they are again larger and more 

 numerous ; in the more crowded portions of the zones there are from six to seven pairs of 

 pores opposite one of the large plates, and where they are more distinct on the sides there 

 are four small pairs opposite one plate. 



The two anterior inter-ambulacral areas are narrower than the posterior pair (fig. 2 a). 

 There are about sixteen plates in a column, each plate forming a double inclined plane, 

 and having its surface crowded with small equal-sized tubercles, arranged close together 

 in three or four rows (fig. 2/) ; the postero-lateral pair are wider and longer, and contain 

 more plates in each column ; in other respects they have a similar structure to the anterior 

 areas. The single inter-ambulacrum is about as wide as the postero-lateral pair ; it is 

 truncated behind, and its border is grooved by the anal valley ; this depression has a 

 uniform width, is concave at its base and upper part, and there is always an undepressed 

 portion of test between its termination and the apical disc (fig. 2 a) ; the anal opening 

 is round, and is seen at the end of the valley (fig. 2 a, d). 



The apical disc is small and excentral ; its elements are so intimately soldered together, 

 that the sutures in all ray specimens are obliterated ; the madriporiform tubercle is large 



* 'Annals and Magazine of Natural History,' 2d series, vol. ix, p. 300. 



