352 Dr. G. J. Hinde on a true Leuconid Calcisponge 



XLVI. — On a true Leuconid Calcisponge from the Middle 

 Lias of Northamptonshire^ and on detached Calcisponge 

 Spicules in the tipper Chalk of Surrey. By GeoeGE 

 Jennings Hinde, Ph.D. 



[Plate XVII.] 



I. On a true Leuconid Calcisponge from the Middle 

 Lias of Northamptonshire. 



Mr. E. a. Walforu, F.G.S., of Banbmy, kindly sent to 

 me some time since for study and description several speci- 

 mens of a small sponge which he had discovered in the Marl- 

 stone beds of the Middle Lias at King's Sutton, near Banbury. 

 The specimens, though small or almost microscopic in size, 

 appear to be perfect and full-grown, and their state of preser- 

 vation is so remarkable as to permit of ready determination 

 of their minute skeletal structures. This is the more sur- 

 prising since the specimens prove to be Calcisponges, as 

 delicate and fragile as any existing representatives of this 

 group. Though occurring in strata of such a comparatively 

 remote geological period, the structure of these specimens so 

 fully agrees with that of existing sponges of the genus Leu- 

 candra^ H^Eckel, that I propose to include them therein. 

 Only a single species has as yet been determined, which is 

 described below under the name of Leucandra Walfordi. 



Leucandra Walfordi^ sp. n. (PI. XVII. figs. 1-9.) 



Sponges small, club-shaped, subcylindrical or compressed, 

 slightly contracted at the base, which is attached to small 

 grains of sand or fragments of other organisms. Usually 

 growing single, but occasionally two or three individuals are 

 attached together at their bases. The specimens range from 

 2 to 3"5 millim. in height and from '6 to 1 millim. in thick- 

 ness. The outer surface is slightly hispid, with obliquely 

 projecting spicules ; the summits are obtusely conical or 

 truncate, without any distinctive neck or spicular collar. 

 The cloacal tube extends nearly to the base of the S))onge ; 

 it opens by a circular or, in the compressed forms, elliptical 

 aperture, from "2 to "5 millim. in width. Tlie inner or cloacal 

 surface of the wall is apparently smooth and without any 

 special layer of spicules. The walls of the sponge are about 

 •2 millim. in thickness ; they are composed of cylindrical or 

 fusiform acerates or rod-shaped spicules and three- or four- 



