NUCULA LUCINIFORMIS. 187 



part very short, and slightly inclined to it. The umbones are tumid, oblique, 

 pointed forwards, contiguous, raised above the hinges, and situated in the 

 anterior quarter of the hinge-line. In front the umbones are excavated by a small 

 cordate lunule. There is a small lanceolate escutcheon behind. The valves are 

 regularly swollen, the greatest convexity being a little above the middle point of 

 the valve ; towards the posterior end the shell is compressed and expanded, 

 especially at the obtuse posterior-superior angle. There is an obscure oblique 

 fold and shallow oblique sulcus immediately in front of it, which pass from the 

 umbo downwards and backwards to the posterior-inferior angle. 



Interior. — The anterior adductor scar is just within the anterior-superior angle 

 of the shell, and separated from the umbo by a deep sulcus. The posterior 

 adductor scar is very shallow, but its anterior edge is linear and deeper. The 

 pallial lice is remote from the margin, and entire. The hinge, according to M'Coy, 

 is normal, but I have not been able to obtain a view of it myself. 



Exterior. — The surface is almost smooth, but under a low microscopic power 

 extremely fine concentric strias, with a few irregular stronger lines of growth, are 

 to be seen. 

 Dimensions. — The type specimen Antero-posterioriy. 



(fig. 18, PI. XIV) measures — 11 mm. 

 Fig. 17, PI. XIV (an abnormally 



gibbose specimen) . 13 mm. 



Fig. 19, PI. XIV . 11 mm. 



Localities. — " Bolland," Yorkshire (Phillips). (The correctness of this I doubt, 

 from the matrix and condition of the shell.) Scotland : the Upper Limestone 

 series ; Gare, Robroyston, and Orchard, near Glasgow : Den, Daliy. Middle 

 Ironstone series, Robroyston, and Bishopbriggs. Lower Limestone series, Lingula 

 Ironstone, Carluke : in shale above the Hosie Limestone, Campsie and Thornton : 

 Roscobie, Fife. 



Observations. — I re-figure the type specimen of this species, preserved in the 

 Gilbertson Collection (Brit. Mus. Nat. Hist.), PI. XIV, fig. 18. It is labelled as 

 having been obtained from the Carboniferous Limestone, Bolland, but the nature 

 of the specimen at once shows that it has never been in a bed of limestone. I 

 have been able to study a fine series of this species from the cabinet of Mr. J. 

 Neilson, of Glasgow, and several of these I figure. The majority are more com- 

 pressed than the type ; but fig. 17, PI. XIV, a shell in the Woodwardian Museum, 

 Cambridge, labelled from the Carboniferous Shale, Glasgow, is quite gibbose. De 

 Koninck (op. cit.) thought fit to refer this species to Cardiomorpha, but figured 

 shells of a character totally different from the type, and he was therefore wrong in 

 identifying his shells with that described by Phillips. M'Coy (op. cit.) states that, 

 to settle the generic character of the shell, he cut down on the hinge-line of a 



Dorso-ventrally. 



From side to side. 



9'5 mm. 







12 mm. 



8 mm. 



8 mm. 



5'5 mm. 



