﻿214 



ECHINOCONUS 



notched with internal auricles, and supporting a pentagonal masticating apparatus ; vent 

 oval, acuminated above, opening on the border, either marginal or infra-marginal. 



Ambulacra lanceolate ; poriferous zones narrow ; pores unigeminal, except near the 

 peristome, where they are trigeminal. 



Inter- ambulacra wide, with numerous primary tubercles, small on the sides and 

 upper surface, and larger at the base ; in both crenulated and perforated ; miliary granules 

 either microscopic and homogeneous, filling up all the intermediate spaces, or larger and 

 more developed, and disposed in regular circles around the primary tubercles. 



The apical disc, placed at the centre of the summit, is quadrangular, solid, and 

 compact, and composed of four perforate and one imperforate ovarial plates ; the right 

 antero-lateral is much the largest, and is prolonged posteriorly with a portion of the 

 madreporiform body into the centre of the disc ; the three other plates are much smaller, 

 and terminate externally in prominent angles, in which the genital aperture is pierced. 

 The five ocular plates are very small, and interposed between the angles of the ovarials. 



The genus Echinoconirs is distinguished from Discoidea by the position of the vent, 

 and the absence of projecting processes from the interior of the test ; from Pyyaster by its 

 infra-marginal vent, absence of a dorsal aperture, and its elevated conoidal test ; from 

 Holectypus by its elevated profile and much smaller mouth- and vent-openings ; from Pyrina 

 in the quadrangular structure of the apical disc, its more pentagonal and conoidal 

 form and regular decagonal peristome provided with five jaws, and by its infra-marginal 

 vent. 



In Professor Desor's valuable Monograph on the Galerites twelve species are beauti- 

 fully and accurately figured belonging to the genus Echinoconus, such as I have defined 

 it ; after a careful study of this series, and a comparison with a collection of specimens of 

 many varieties now before me, I have come to the conclusion that they all are referable 

 to four types, each of which may be described as a distinct species. These are — 



1st. E. castanea. — Has an oblong form, enlarged anteriorly and contracted posteriorly ; 

 the upper surface depressed ; it belongs to the Upper Greensand, the Chalk-marl, and 

 Lower Chalk. 



2nd. E. sub-rotundus. — Has a tall, round, or sub-globular test, and appears to be one 

 of the many forms which were figured by Klein and described by Leske under the name 

 Echinites vulgaris ; the specimens grouped together were siliceous moulds, entirely destitute 

 of shell, and clearly referable to several specific forms ; one of them may represent the 

 beautiful test I have figured ; but as it is impossible to determine its identity, I prefer 

 retaining the appropriate name given to it by Mantell. This species is collected from 

 the Lower Chalk of Sussex, and several of my specimens came from Lewes. 



3rd. E. conicus. — This is the true Eciiinoconus vere conicus ; marino-lerrestris, 

 creta repletus ; ex creta fodinis Cantianis, of Breynius ; two years later Klein named it 

 Comdus albogalerus on account of its fancied resemblance to the white caps worn by the 

 priests of Jupiter; it has been frequently figured (see the synonyms of this species) and 



