BRITISH FOSSILS. 



Decade IY. Plate I. 



TEMNECHINUS EXCAVATUS. 



[Genus TEMNECHINUS. Forbes (1852). (Sub-kingdom Eadiata. Class EcMno- 

 dermata. Order Ecliinoidea. Family Echinidse.) Body spheroidal; ambulacral and 

 interambulacral segments developed, bearing on their plates, whose sutural margins 

 are excavated but not perforated on the dorsal surface of the test, tubercles of various 

 sizes, imperforate and placed on smooth bosses. Vent in the centre of the prominent 

 apical disk, which is composed of five genital and five ocular plates, all perforated. 

 Ambulacral avenues composed of pairs of pores indistinctly ranked ; the ranks confluent 

 throughout. Mouth central, inferior, armed with a powerful dental lantern. Spines of one 

 order, but of various sizes.] 



Synonyms. Temnopleurus excavatus, Searles Wood, in Morris Cat. 

 Brit. Foss. p. 60. (1843.) 



Temnopleurus Woodii, Agassiz, Cat. Rais. des Echin. in Ann. Sc. Nat. 

 3d series, t. vi. p. 360. (1846.) Temnechinus excavatus, Forbes, Brit. 

 Tert. Echin. p. 6, pi. 1, fig. 1. [published by the Palseontog. Soc.] (1852.) 



Diagnosis. T. corpore depresso, superne subexcavato, sulcis suturalibus 

 profundis conjluentibus. 



It is very remarkable that a group of Echinidse differing 

 essentially and generically from any known assemblage should be 

 characteristic of the Coralline and Red Crag formations of England, 

 and at present be known only as confined to them. The type of 

 this genus is the form here described. I have named the group 

 Temnechinus (ts/hvo^, incisus, and sxi^yos). 



This beautiful Echinite was originally named by Mr. Searles 

 Wood and placed by Professor Agassiz in his genus Temnopleurus, 

 under which it was enumerated by Mr. Morris in his catalogue. 

 But Temnopleurus has imperforated tubercles elevated upon 

 crenulated bosses, a striking and easily recognized character, shared 

 also by Salmacis. Temnechinus accordingly will hold a position 

 intermediate between these genera and Echinus strictly so termed. 

 In the arrangements of its genital disk it exhibits considerable 

 peculiarities of its own. Its spines resemble more nearly those of 

 [iv. i.] .4b 



