36 THE FOSSIL ECHINOIDEA 



Locality. In the Eanikot series, hills east of Lynyan,. from the brown limestone. 

 Survey-number G ^-|^. 



Illustrations of the Species in Plate VIII. 



Fig. 1. Acanfhechinus nodulosus, Duncan & Sladen. The remains of the test, 

 natural size. 



2. Ambulacral and interradial plates at the ambitus : magnified. 



3. A primary tubercle : magnified. 



SubfamiJy TEMNOPLEUBID^. 



This subfamily, on account of the late discovery of other fossil and recent forms 

 than it formerly comprehended, must be considerably enlarged. A critical examination 

 of the genera and species hitherto included in the subfamily, and a careful morpho- 

 logical study of one group of the genera, necessitate its division into two groups, which 

 probably may each form a subfamily. It is unfortunate that the genus Temnopleurus, 

 which is not represented by species in the Nummulitic series, and which is apparently 

 a recent development, should have given the name to the subfamily, many of the 

 genera of which are found fossil. The morphology of the test of the genera Temno- 

 pleurus, Salmacis, Amblypneustes, and PleurecJiinus * is peculiar, and the true pits at 

 the sutural angles undermine the test, whose plates are united by knob and socket 

 suturing. These morphological details are not found in Temnechinus and the forms 

 found fossil in the Nummulitic of Sind, although some of them have been classified as 

 species of Temnopleurus. 



Nothing is more distinct than the structure of the outside of the test of the genus 

 Temnechinus, and the genera we associate with it, and that of the genus Temnopleurus 

 and the genera already noticed in relation to it. In the one the raised ornamentation 

 produces the appearance of depressions along the whole line of the sutures, especially 

 of the horizontal sutures ; and in the other there are, besides, deep pits at the sutural 

 angles and a special method of union of the plates. The structure of the apical system 

 is peculiar in some of the genera associated with Temnechinus, and difi"ers from that of 

 Temnechinus itself. The apical system of the Temnopleurids with true pits appears 

 to be tolerably uniform, and to be fashioned upon the plan of Temnechinus. Crenu- 

 lation and non-crenulation of the tubercles exist in both of the groups. 



We have had the advantage of examining a very perfect specimen of a Qlypho- 

 cyphus from the Upper Greensand of England, and also of studying the plates of other 

 species drawn under the direction of Cotteau and Wright. Our form is clearly of the 

 subfamily Temnopleuridse ; but it does not belong to the group with true sutural pits, 

 but to that with Temnechinid sutural depressions. 



The diagnosis of Glyphocyphus is given in d'Archiac and Haime's ' Animaux 



* P. Martin Duncan, Journ. Linnean Soc. vol. xvi. p. 243, 1882, and ibid. p. 448. 



