394 On the Genus Tellhiomya^ and allied Genera. 



Genus Ndculites. — Conrad, 1841, Geological Report of New 



York, page 49. 



" Equivalved ; hinge, with cardinal teeth, as in Nucula, but 

 apparently uninterrupted beneath the apex ; an interior rib like 

 that of Solecurtus, but narrower, extends from the apex, either 

 direct or slightly oblique, towards the base, never passing much 

 beyond the middle of the valve." 



" These shells have much the exterior aspect of Nucula, but the 

 deep sinus in casts of some of the species, left by the interior rib, 

 constitutes about the same amount of difference between the two 

 genera as between Solen and Solecurtus, especially, as I believe to 

 be the case, that the series of cardinal teeth is uninterrupted by a 

 fosset, which in Nucuia is a prominent character. This genus, so 

 constituted, is restricted to the Silurian, and perhaps to the Carbo- 

 niferous system." 



Genus Cucullella. — McCoy, Ann. Nat. Hist., 2d series, vol. vii., 

 p. 50. British Pal. Fossils, p. 283, 1855. 



" Generic Characters. — Sub-rhomboidal, inequilateral, sub- 

 equivalve ; margin, even ; hinge line, entirely crenulated ; muscular 

 impressions, two, with a simple pallial scar between them ; a strong 

 internal septum extends from before the beaks to the posterior 

 margin of the adductor muscle, forming a deep slit in the casts ; 

 surface, generally smooth, or nearly so." 



" These Palaeozoic shells have been confounded with Nucula^ 

 (Sow., Phil., (fee.,) from which they differ in the absence of the 

 ligamentary pit in the hinge, and in the anterior internal septum ; 

 they have also been confounded with Cucullea, from which they 

 differ in wanting the hood-like plate of the posterior adductor, and 

 having the septum in the anterior end ; and with Clidophoi-us, 

 (Geol. Surv. of Great Britain,) from which they differ in having 

 the hinge crenulated as in ArcaP 



The genus Lyrodesma of Conrad was constituted to receive a 

 small shell which occurs in the shales of the Hudson River group, 

 and which, but for certain restrictions in the generic description, 

 might include those here referred to Tellinomya. 



Lyrodesma. — Conrad. 



Generic Characters. — "Equivalved, inequilateral ; hinge line, 

 with eight diverging prominent cardinal teeth, transversely 

 striated." 



