344 PEOr. p. M. DUNCAN' ON THE MOEPHOLOGT 



three types. The second type he made to comprehend the genus 

 Temnopleurus, Agass., and its allies, they being Echini with sculp- 

 tured tests and ornamented with fossettes, or little cavities, at the 

 angles of the plates. Their pores might be unigeminate or bige- 

 minate *. This type has been called a subfamily of the family 

 Echinidse by A. Agassizt, and the name of Desor has been 

 appended to it. It has received much attention from nearly every 

 naturalist who has studied the Echinoidea, and especially because 

 some of the genera have persisted from the commencement of the 

 Tertiary ages to the present day. 



There have been ten genera associated with the subfamily, some 

 of which belong to it without doubt ; and the classificatory posi- 

 tion of the others has been debated or enlarged upon by Desor, 

 Lijtken, and A. Agassiz, These authors, and also L. Agassiz, E. 

 Eorbes, Jules Haime, D'Archiac, Loven, and Bell, have contri- 

 buted to our knowledge of the superficies of the test of many 

 of the species of the subfamily. 



During the last twelvemonth a very large collection of fossil 

 Echinoidea from Sind has been entrusted to Mr. Sladen, E.L.S., 

 and myself, by the Superintendent of the Geological Survey of 

 India, for description ; and amongst those specimens which had 

 been derived from the Eocene rocks there were many which would 

 be called Temnopleuridse, and some forms which required very 

 careful consideration before they could be classified therein — 

 such, for instance, which had a ribbed ornamentation around the 

 primary tubercles and extending across the median space of the 

 interradials, the spaces between the ribs resembling those drawn 

 by A. Agassiz in Trigonocidaris. But the spaces were not really, 

 to my mind, either sutural impressions or little cavities at the 

 angles of the plates. In fact, I found the classificatory difficulties 

 great. 



Wishing to have some definite information concerning the 

 morphology of the cavities at the angles of the plates and the 

 meaning of the sutural depressions, I sought for information in 

 the writings of my predecessors, and obtained recent specimens 

 from the southern coast of Sind. The desired information has 

 been found exceedingly meagre. In fact, so far as I have been 

 able to discover, no one has examined the deeper connexion of 



* Desor, ' Syn. Ech. Foss.' p. 60. 



t A. Agassiz, 'Eevision of the Gfenera of Echini,' p. 460, 



