200 CARBONIFEROUS LAMELLIBRANCHIATA. 



Interior. — The anterior adductor scar is small and marginal ; the posterior, 

 inconspicuous, is situated within the dorsal slope. The pallial line is very slightly 

 marked, and no sinus can be seen. There is an internal subumbonal, shallow, 

 and narrow ridge, extending from the umbo downwards to the inferior border. 

 The hinge has as yet not been observed. 



Exterior. — The surface is ornamented with very fine, regular, concentric strias, 

 hardly visible to the naked eye. These become somewhat coarser near the inferior 

 border. At the posterior end the stries disappear, and the markings assume the 

 form of fine waves and fluctuations. 



Dimensions. — Fig. 17, PL XV, measures — 



Antero-posteriorly . . . .13 mm. 



Dorso-ventrally . . . .7*5 mm. 



Elevation of valve . . . .2 mm. 



Localities. — Scotland : Upper Limestone Series, Garngad Road, Glasgow. 

 Calciferous Sandstone series in Black Shale, Woodhall, Water of Leith. 



Observations. — This species, described from the Calciferous Sandstone series of 

 the neighbourhood of Edinburgh by Mr. R. Etheridge, jun., appears to come 

 midway between N. attenuata, Fleming, and N. Isevistriata, Meek and Worthen, 

 possessing the attenuated posterior end of the former, and the compressed form 

 and narrow escutcheon of the latter. From N. attenuata, N. Sharmani is easily 

 separated by the narrow escutcheon and less produced and rostrated posterior 

 end. Of all figured shells, N. birostrata, M'Coy, approaches most nearly to the 

 species under discussion, but unfortunately the type specimen has disappeared, 

 and I am unable to trace that shell. Mr. Neilson of Glasgow has discovered in the 

 neighbourhood of Glasgow a few specimens which I refer to this species, and 

 some of these I figure, PI. XV, figs. 17 and 18. 



Mr. Etheridge compared his specimens with several of M'Coy's figured 

 specimens. He says that " from Nucula (or Lecla ?) birostrata, M'Coy, it is 

 distinguished by its straighter posterior end and larger antero-ventral development ; 

 from Nucula (or Lecla?) clavata, M'Coy [figure only], by the more central position 

 of the beaks, and longer anterior end. From Nucula (or Lecla?) leiorhynclia, 

 M'Coy, the ornamentation of the posterior end will at once distinguish it." My 

 own observations lead me to think that this last distinction is an error, and that, 

 in common with other Carboniferous Nuculanx, both N. Sharmani and N. leio- 

 rhynchus have similarly ornamented posterior ends, the concentric strias terminating 

 abruptly as in N. attenuata, Figs. 2 — 4, 6, and 7, PL XV. M'Coy distinctly 

 shows this to be the case in his enlarged figure of N. leiorhynchus ; and whether or 

 no M'Coy's species is synonymous with the species under discussion depends on 

 the size of the escutcheon, which I have not been able to get at, the type specimen 

 being a small and very poor example. For the present I have doubtfully placed 



