29 



ambulacra, formed by four rows of pores, connected by transverse lines, 

 each two rows, uniting at the end of thegrooves. Two of the ambu- 

 lacra, the shortest, are directed obliquely towards the narrow truncated 

 extremity ; two others, longer, pass obliquely towards the broader end ; 

 and the fifth passes straight to the mouth, forming the dorsal groove. 

 Along the middle of the opposite part, a keeled edge passes directly to 

 the anus. The vertex is perforated by four large pores. The mouth is 

 reniform ; the upper lip triangular, and extended over the lower. The 

 anus is round, and placed in the upper margin of the acute extremity. 

 From the anus, a slight depression passes to the lower margin ; at each 

 of the angles of which is a protuberance, surrounded by a broad smooth 

 surface. 



Specimens of this species are found in many parts of Europe, but 

 particularly in Germany and in England. They are the most frequent 

 fossils in the chalk-pits of Kent and Essex, and are frequently found 

 filled with flint. These are the Echinites cordati vulgares of Lhwydd, 

 Lithoph. Fig. 964967. 



Two more varieties are noticed by Leske : the one, sulcis crispis, does 

 not, in the figures referred to, appear to possess this particular charac- 

 ter ; and the other, norvagicum, Tab. xxm. E. F. Klein, varies from the 

 preceding, in being a little more oblong in its form. 



Spatangus lacunosus, Tab. xxui. A. B. Tab. xxiv. a. b. and Tab. xxvu. 

 A. Klein. This fossil, which has indubitable claims as a distinct species, 

 is of an oval form; its upper surface gibbous, and its under rather con- 

 vex. At the vertex are two, or, according to Muller, four puncta. 

 From the vertex immediately proceed four deeply sulcated obtuse am- 

 bulacra, with angular margins: within the grooves are four rows of 

 pores, connected by transverse lines. The two posterior ambulacra, 

 directed towards the narrower part of the shell, are shortest, being 

 sometimes merely two deepish fossulse : between the two anterior am- 

 bulacra is disposed another deep groove, which is also beset with striae 



