514 PROCEEDINGS OF THE ACADEMY OF [Dec, 



Pecten (Amusium) luna n. sp. PI. XXIII, fig. 1. , 



A species resembling P. mortoni Conr., from which it differs chiefly 

 by the ears which are depressed below the plane of the valve and 

 separated by a ledge. In P. mortoni the ears are nearly level with 

 the adjacent part of the valve, from which grooves separate them. 

 The hinge-line is short, not serrate above in the right valve, as in 

 P. mortoni. The surface is smooth throughout except for the usual 

 hue growth-lines and fine, indistinct radial striation, such as is seen 

 in P. mortoni. The laterodorsal lines diverge more than in mor- 

 toni, forming a greater angle at the beak. The internal ribs run in 

 pairs, spaced about as in P. sol. The shell is rather strongly convex 

 for an Amusium, more convex than in P. mortoni. 



Alt. 76, length 80 mm.; diam. right valve 12 mm. 



Gatun Formation at the Spillway. 



The type is a right valve, which we at first referred to P. sol, 

 from which it differs chiefly by the unsculptured beak and the 

 ledges defining the ears. 



P. ioulce differs by its gray radii. 

 Spondylus scotti n. sp. PI. XXV, figs. 1, 2. 



A species of the S. americanus group, having the lower valve 

 very convex, the upper valve moderately so; beak not much produced. 

 Sculpture of about 17 narrow little-prominent radial ribs, some 

 of them bearing very short, scale-like spines, irregularly placed, 

 and on the lower half only; between these ribs there are fine, un- 

 equal longitudinal striae, 4 to 8 in each space. They are crenulated 

 by extremely fine, crowded laminae along the growth-lines. There 

 are some weakly developed foliations on one side of the lower valve. 



Breadth 51 mm., length (alt.) of lower valve 65, of upper 58 mm., 

 diam. 41 mm. 



From the lignitic bed below the Pecten bed at Tower N, Culebra 

 Cut, 



Well distinguished from the recent Antillean S. americanus 

 Hermann by the delicacy of the sculpture and more convex lower 

 valve-. It is also somewhat related to S. gumanomocon 4 of the 



* Spondylus gumanomocon n. sp. A species resembling S. varians Sowb. 



S. delessertii Chenu). The upper valve is Pectiniform, orbicular, of moderate 



thickness, with low radial ribs, the principal ones irregularly spinose, spines 



-hurt; cardinal urea small and short, as in S. americanus. Lower valve very 



ponderous, with a long, level (not receding) cardinal area, and a very long, 



Jit (or sometimes laterally curved) beak, the cavity of which is deeply 



sxcavated in young shells, nearly solidly filled in old ones. Sculpture like the 



upper valve, except that it is more or less extensively foliated towards the beak. 



Length (alt.) of a lower valve 175 mm.; breadth 108 mm.; weight 32^ oz. 



anto Domingan ( )ligocene. This is the form identified by Gabb as Spondylus 



