460 ME. H. BOLTON ON" A MAEINE FAUNA IN THE [Nov. 1QC>7, 



Two other internal casts of fine shale show that hoth posterior 

 and anterior adductor muscle-scars must have been present as 

 moderately-deep pits, the posterior being the deepest — so deep, in 

 fact, that a film of the shale-cast has remained behind attached 

 to the shell. The small punctate scar of a pedal muscle lies nearly 

 midway between the adductor-impression and the umbo, the cast 

 of the latter being marked by a shallow fissure, in which are two 

 small tubercles indicating the position of corresponding pits in the 

 shell. 



ISTuctjlana acuta, Sowerby. 



Very few examples of this species were found. The elongation 

 and attenuation of the posterior extremity are clearly shown, both 

 in casts and in the shell. 



At Ashton Yale this is a more robust and larger shell than Nu- 

 cula cequalis, and is also more produced anteriorly than the latter. 

 There is hardly any likelihood of confusion between the two forms. 



Tellinomoepha (?) 1 Hindu, sp. nov. (PL XXX, figs. 8 a & 8 b.) 



Examples of the present species are fairly numerous, but can 

 rarely be freed from the matrix, which usually adheres to the 

 anterior portion of the shell. 



Diagnosis. — Shell somewhat quadrangular in outline, with 

 tumid umbones, from which a strong subangular ridge passes 

 obliquely backwards to the inferior border. The hinge-line inclines 

 slightly downwards in front of and behind the umbones, and thus 

 encloses a wide or obtuse angle. The shell is hollowed out in 

 front of the umbones in the best-preserved examples, so that the 

 anterior margin appears to commence low down below the umbo. 

 The anterior margin is well rounded, and passes directly into the 

 ventral margin, which forms a wide curve downwards and back- 

 wards until it meets the oblique ridge, at that point passing 

 upwards into the slightly-curved posterior border, which inclines 

 a little inwards to meet the hinge-line. 



The surface of the valves is smooth, and thrown into irregular 

 transverse corrugations crossed by fine concentric strise. 



Only the anterior fourth of the shell lies in front of the middle 

 line of the umbo. We have not been able to secure a good interior, 

 so that the structure of the hinge is not yet known. 



Paeallelodon tentjisteiatum (Meek). 2 (PI. XXX, fig. 12.) 



Only one internal cast of this form was found, which 

 Dr. "Wheelton Hind kindly identified. The cast indicates a strongly- 

 gibbous shell, marked by concentric lines of growth, most evident 



1 Dr. Hind, who has kindly given me the benefit of his criticism and advice 

 upon the kmellibranchs, is strongly of opinion that this species belongs to the 

 genus I'ellinomorpha, although my own observation leads me to the conclusion 

 that it is more nearly allied to Parallelodon. 



2 Final Eeport U.S. Geol. Surv. Nebraska, 1871, pt. ii, p. 207 & pi. x, 

 figs. 20 fl-20 b. 



