﻿FROM THE UPPER GREENSAND. 



249 



D'Orbigny lias separated the latter into a distinct genus under the name Trematopygm % 

 all of which are special to the Cretaceous Rocks ; and they form a convenient section of 

 the genus, although the characters on which the separation is based are, from my point of 

 view, too slight and evanescent to form a stable generic basis. The apical disc is small, 

 quadrate, and compact ; it is composed of four perforated and one imperforate genital plate, 

 the right antero-lateral, supports the madreporiform body ; the five oculars are very small 

 and triangular, and are wedged in between the genitals and apices of the lanceolate 

 ambulacra. 



The tubercles are small, with perforated summits and depressed areas, and the 

 surface of the plates is covered with microscopic granulations. 



The genus Echinobrissus was established by Breynius in 173.2 in his important 

 memoir ' De Echinis et Echinitis,' and of which I have given a translation at p. 193. 



Klein, who published only two years afterwards, did not, unfortunately, preserve the 

 well-defined genera proposed on such good characters by his learned contemporary ; 

 and Leske, his commentator, in 1778 placed the Echinobrissus of Breynius under the 

 Spatangus of Klein. When Lamarck in 1801 proposed the genus Nucleolites in the 

 first edition of his great work, he was not aware that the same group of Urchins had 

 been well figured and accurately diagnosed sixty-nine years before by Breynius ; but in 

 the second edition of ' Animaux sans Vertebres ' a reference was made to this work for 

 figures of the species. The late Professor Agassiz in dismembering Lamarck's Nucleolites 

 unfortunately did not restore Breynius' genus, although, as a rule, Agassiz adhered to the 

 genera of the older naturalists. To the late Professor A. d'Orbiguy the honour is due 

 of vindicating the claims of Breynius's work, and which all subsequent Echinologists, 

 Desor, Cotteau, and De Loriol, have rigidly observed. 



Echinobrissus lacunosus, Goldfuss, 1 1S29. 



Nucleolites lacunosus, Goldfuss. Petref. Germanise, pi. xliii, fig. 8, p. 141, 1S29. 



— — Desmoulins. Etudes sur les Echinides, p. 3GU, 1837. 



— — Morris. Cat. of Brit. Foss., p. 55, 1843. 



— — Agassis et Desor. Cat. raison., p. 97, 1847. 



— — Forbes. Mem. Geol. Survey, Decade i, p. 8, 1849. 

 Echinobrissus — oVOrbiyny. Pal. Franc. Ter. Cret.,pl. 958, figs. 7 — 10, 1855. 



Diagnosis. — Test ovate, obtuse anteriorly, subquadrate and subtruncate posteriorly, 

 sides subcompressed ; upper surface convex, vertex subcentral or supra-anal ; ambulacra 

 narrowly lanceolate; anal sulcus deep, short, oblong, and abruptly declined; inter- 

 1 No specimen has been found hitherto sufficiently perfect for the purpose of illustration. 



32 



