304 CARDI ASTER. 



with a crenulated summit, on which is placed a perforated tubercle (fig. 2 /). Very 

 fine, close-set, homogeneous granules are prolonged horizontally between the pairs of 

 pores in the poriferous zones, and likewise fill up the anteal sulcus, which is completely 

 deprived of primary tubercles (fig. 2 e and d). 



The apical disc is narrow, solid, and elongated, and so closely covered with the small 

 granules that its elements are concealed. In many specimens it is composed of four 

 ovarial and five perforated ocular plates. The anterior ovarials are small, and the madre- 

 poriform tubercle is quite rudimentary. The postero-laterals are long, and separated 

 from the anterolaterals by two perforated oculars, so that the three anterior ambulacra 

 are rather widely separated from the two posterior ambulacra (fig. 2d). 



The vent opens very low down in the narrow, posterior, triangular border. The 

 periprocte is widely oval, and surrounded by numerous small granules (fig. 2d). 



The marginal fasciole is more or less distinct in different specimens. It passes under 

 the periprocte, and runs out upon the sides towards the convex portion of the ambitus. 

 It is narrow, and free from intermingled tubercles (fig. 2 g), and it is only well seen in 

 very good specimens. 



The base is flat, and the mouth situated near the anterior border in a depression 

 formed by the deep grooving of the anteal sulcus, where it turns round the anterior 

 border (fig. 2 b, e). The peristome consists of a convex upper lip and a prominent under 

 lip. A few tubercles make a radiate ornamentation about the upper lip (fig. 2 b). 



Affinities and Differences. — Cardiaster ananchytis is well distinguished from its 

 congeners by its cordiform outline dilated before and subangular behind, by its deep 

 anteal sulcus deprived of tubercles, by the poriferous zones very unequal in the antero- 

 and postero-lateral pairs, by the large tubercles which show themselves sparsely on the 

 upper surface, and by the low position of the periprocte. 



History. — Leske (177S) first figured an imperfect specimen of this Urchin under the 

 name of Spatangus ananchytis, and Lamarck afterwards called it Anancliytes cordata. 

 Goldfuss figured it under the name of Spat any us granulosus, and S. orbicularis. Mr. 

 Samuel Woodward, in his ' Geology of Norfolk,' figured it as Spatangus cordiformis ; 

 and then succeeded the various changes of name which have been already noted in the 

 synonymy of the species. It is, however, to M. d'Orbigny's quick perception that we are 

 indebted for first identifying Leske's figure with the subject of this article. 



Locality and Strati graphical Position. — First identified as a British Urchin by 

 Mr. S. Woodward, who stated that it was rare in the Upper Chalk at Harford Bridge, 

 and common in the Medial Chalk at Swaffham and Thetford, Norfolk. General 

 Portlock has found and described it as Ilolaster aqualis in the Chalk of Londonderry. 



Foreign Localities. — It has been collected in France, where it is rare, at Chateau-du- 

 Loir, Teiffe, Duneau, Villedieu, Sarthe ; Tours, Indre-et-Loire ; Lauquais, Dordogne ; 

 Meudon, Seine : at Ciply, Belgium ; Langelsheim, Brunswick ; Haldem, Westphalia, in 

 North Germany: it is found in the Upper and Lower Sennnian. 



