SCALDIA. 89 



is absolutely covered with tlieir crowded valves, though so decayed and often so 

 distorted that they cannot be individually recognised, and it is only by means of 

 an occasionally better preserved specimen that the species can be made out. The 

 totally different appearance sometimes produced by the extreme distortion is 

 illustrated by the two figures on PI. X, which were not recognised as the present 

 species till long after they were drawn. 



Affinities. — From the two accompanying species of this genus the present shell 

 is at once distinguished by its long lancet-like shape and its angular posterior side. 

 It appears confined to the Sloly beds, while the other two occur higher in the 

 series, the one near the base, and the other in the middle of the Pilton beds. 



It is something like Gtenodonta tumida, Sandberger,^ in general shape, but is 

 totally different in detail. 



2. Order— HOMOMY ARIA; Zittel, 1881. 



I. Family — Unicarditd.e, Fischer, 1887. 

 1. Genus — Scaldia, de ByckJiolt, 1847. 



I have placed the following species under this genus as being possibly in accord 

 with it, but sufficient is not known of the shell to determine its true affinities. 



1. Scaldia? longa, n. sp. Plate X, figs. 1, la, 2. 



Description. — Shell small, transversely oval, very convex. Umbo nearly central, 

 prominent, slightly arching forward. Anterior and posterior margins nearly 

 similar and approximately semicircular. Inferior margin gentlj convex. Contour 

 rather flat transversely, very convex vertically, becoming concave in the superior 

 corners. Umbonal slopes rounded. Muscle-scars extremely large, irregularly 

 subcircular, situated on the superior side not far from the umbo. Shell-structure 

 very thick. 



Size. — A single valve is about 12 mm. long, 9 mm. high, 3 mm, deep. 



Localitij. — Two specimens are in the Museum of Practical Geology from South 

 Cave, Baggy Point, 



Bemarhs. — The nearly central umbones and sub-equilateral transversely oval 

 form distinguish these little shells from any that otherwise approach them. 



^ 1853, Sandberger, ' Verst. Ehein. Nassau,' p. 277, pi. xsix, figs. 6, Ga. 



M 



