108 W. S. SucUeston — On the Yorkshire Oolites. 



smooth and almost polished, except where there has been a decor- 

 tication of the outer layer of shell. This decortication, besides 

 affecting a considerable area near the outer lip, has formed a belt 

 in the posterior region of the base, thus producing a sort of false 

 carination. In this way we learn that both inner and outer layers 

 of shell were of considerable thickness. (N.B. — The shell is now 

 mainly in the condition of spathic iron, coated and coloured with 

 brown oxide). 



The columella and anterior extremity of the aperture have, in 

 like manner, suffered some injury, producing an exaggerated appear- 

 ance of an umbilicus. As far as one can judge from present condition 

 the aperture is almost quadrate. 



Description of another specimen. — Same horizon and locality. 

 Leckenby Collection (Fig. 2). 



Length (restored) 38 millimetres. 



Width 13 „ 



Eatio of body-whorl to entire shell 37 : 100. 



Spiral angle 29°. 



There are 8 whorls, with fairly-preserved outline, but these have 

 all suffered from attrition, or some other cause, so that we do not 

 see the outer shell layer as couipletely as in the specimen from the 

 Bean Collection. In consequence, the convexity of the whorls is 

 slightW less marked, the sutures are shallower, and the proportion 

 of width to height is less : the traces of the wavy longitudinal lines 

 are very slight. On the other hand, the aperture, though consider- 

 ably involved in matrix, has an outline somewhat better preserved. 

 Its resemblance to that of some Nerinoeas is rather suggestive. 



Belations and Distribution. — This form seems to be confined to the 

 Dogger, where it is rare, no other specimens having come under my 

 notice. Its affinities are difficult to trace, as it appears to have no 

 near relations either in this or in higher horizons. Whether there 

 are any forms in the Lias which could be regarded as related, I am 

 unable to say ; but certainly, as regards the Yorkshire Lias, Tate and 

 Blake make no mention of any such shell. It would be hazardous 

 to venture on any conjecture as to its relations in the foreign beds, 

 inasmuch as we are not in a position to ascertain beyond a doubt 

 the true character of the aperture. I would merely allude to the 

 possibility of its connection with the genus Fibula, Piette (Bull. 

 Soc. Geol. France, April 20, 1857), founded for the reception of 

 cei'tain peculiar Ceritliia occurring in the Bathonian of the Aisne 

 and the Ardennes. A rudimentary umbilical groove is one of the 

 characteristics of Piette's genus, cf. Fibula undulosa, Piette, op. cit. 



Genus Nerin^a. 

 A peculiar interest attaches to the Nerinoeas of the Inferior Oolite, 

 since they are the earliest of their kind. The genus, we are told by 

 Sharpe, usually occurs in calcareous strata associated with shallow- 

 water shells. Thus we do not find Nerinceas in the Lias nor in the 

 Striatuhm-heds, nor even in the Dogger Sands. Indeed I am not 

 aware that any remains of the genus have been detected in the 

 lower portions of the Dogger itself, such as the nodule beds which 



