122 EOCENE MOLLUSCA. 



Spec. Char. N. testa ovata, vix elongatd, gibbosd, laevigata, subintsquilaterali ; pedi- 

 regione rotundatd j siphoni-regione oblique t run cat a v el obtuse rostratd ; umbonibus depressis; 

 m argin ibus cren ulatis. 



" Shell suborbicular, transverse, gibbose, smooth ; extremities pointed ; beaks nearly 

 central, margin obtuse, edge toothed." — /. Soioerby. 



Length, % an inch. 



Locality. Hampstead Heath {Wether ell) ; Highgate, Sheppy ? [Edwards). 



" The radiating structure of this Nucula, common to the species of the genus, is very 

 conspicuous, but the inner surface is not striated, as in N. Bowerbankii." — J. Soicerby. 



The specimens of this species that I have seen are not numerous, and, unfortunately, 

 thev are not in perfect condition ; the umbones are excessively eroded, thereby reducing 

 their natural proportions, giving a slightly rounded outline to the shell. 



Since the type for the preceding descriptions has been set up, several specimens 

 belonging to this genus have come under my inspection, which I cannot assign to any of 

 the foregoing species ; and although they do not present characters sufficiently determinable 

 for specific isolation and description, they are, I conceive, fully deserving of representation 

 and notice, and I propose here to give to them provisional names only until the}" can 

 hereafter, by the possession of more specimens, be satisfactorily characterised. 



Tab. XX, fig. 10, represents the interior cast of a shell from Clewer Green, near 

 Basingstoke, kindly lent to me by Mr. Prestwich, and to which I will give the name of 

 N. venusta ; it appears to have possessed a smooth margin to the edge of the valves, and 

 it has a very slight basal projection on the siphonal side ; there is a prominence in the 

 anal region, and in its contour it is intermediate between N. bisulcata and N. pralonga, 

 but to neither of those smooth-margined species can it, I think, be referred. The age of 

 the deposit in which it is found being greater than that of the two other species strengthens 

 the supposition that this is distinct. 



Tab. XX, fig. 7, is the representation of a specimen, also from Mr. Prestwich's cabinet, 

 to which the locality Cuffells is attached ; this appears to be different from any of the 

 foregoing, but it is imbedded in the matrix, and I am unable to describe its true characters. 

 I give it the name of N. consobrina ; in outline it somewhat resembles N. consors, from 

 Highgate, but is, I think, too long and too much truncated for that species ; it has a very 

 slight elevation in the anal region, but there is no perceptible lunule, although there is a 

 slight depression on the dorsal surface extending from the umbo to the verge of the pedal 

 extremity ; the shell is thick, nacreous within, and the denticles are large, twenty-four on 

 the pedal side, and seven or eight on the other. 



Tab. XX, fig. G, represents a specimen very recently obtained from the Woolwich 

 series at Bickley, by Chas. A. Meyer, Esq. ; this shell has been kindly submitted to my 

 examination. It is probably distinct, and I will call it for the present N. gracilenta ; its 

 nearest relative appears to be N.fragilis, but on a comparison with specimens of that 



