112 It. ETBEEIDGE, JTJ2*., ON ASTKOCKINITES. 



point a small pit, which appears to be the socket of an appendage 

 quite distinct from the pinnule. The groove does not reach the 

 socket of the pinnule, which is situated farther out, between two 

 of the poreSo On the other hand, a small groove runs from each pore, 

 inward, and terminates at another socket, about halfway between 

 the pore and the main median groove of the ambulacrum" *. If the 

 description of the pseudambulacrum of A ? Benniei be referred to 

 (ante, p. 107) and fig. 17 examined, a close affinity to the foregoing 

 will be reccgnized. The sockets at the termination cf the short 

 lateral grooves (c, fig. 17), I think, represent the small pits de- 

 scribed by Mr. Billings in P. pyriformis as terminating the lateral 

 grooves " at a point between the inner extremities of two of the 

 pores." The socket (d, fig. 17), on the other hand, at the end of 

 the groove (/, fig, 17), running inwards from each pore (e, fig. 17), 

 is similar to those in P. -pyriformis, " about halfway between the 

 pore and the main median groove of the ambulacrum." 



As previously stated, the Blastoid affinities of Astrocrinites (-=.Zy- 

 gocrinus) have been pointed out by Dr. F. Rb'mer, Prof, de Koninck, 

 M. le Hon, and the late Prof. Pictet. It is to this order that I 

 would provisionally refer Astrocrinites, at any rate until further evi- 

 dence, obtained from the examination of more perfect specimens 

 than ours, can be adduced for or against such a reference. 



4. Affinities and Differences. 



With the B\'dstoide& Astrocrinites agrees (1) in the nature and func- 

 tion of certain of the plates of the calyx, (2) in the nature, arrange- 

 ment, and mode of growth of the pseudambulacra, (3) in the 

 possession of a central ventral aperture, around which the latter 

 radiate, (4) in the presence of a second ventral aperture, excentric 

 and interradial, closed by a valve or lid. On the other hand, this genus 

 differs from the Blastoidea (1) in the quadriradiate arrangement of 

 its parts, (2) its free and unattached habit, (3) the presence of the 

 tubercular ornamentation ; added to which the typical species has been 

 described as possessing a madreporiform body, which ours does not. 



5. Localities and Geological Horizon. 



Astrocrinites ? Benniei was first found by Mr. Bennie at Carlops 

 Quarry, near Carlops, Peeblesshire, in shale overlying the No. 2 

 limestone of the Lower Carboniferous Limestone group of the Mid- 

 lothian Carboniferous Series, where it occurs in considerable numbers. 

 It was subsequently found plentifully in a bed of shale occupying 

 the same geological horizon at Kidlaw, near Gifford, Haddingtonshire, 

 and more sparingly at East Salton and Salton lime- works, chiefly 

 as fragments ; again at Skateraw and East Barnes, near Dunbar, 

 in the same horizon, but usually in a fragmentary condition. A few 

 individuals were found in the shale overlying the No. 2 limestone 

 at Lampland, near Path-head, Haddingtonshire, and two fragments 

 at Roscobie, Fifeshire, in shale connected with one of the lower 



* i.e. p. 114. 



