1921] . NATURAL SCIENCES OF PHILADELPHIA. 413 



narrow tops of the ribs are a little flattened. Ears wanting in the 

 type.v It is a good deal like the right valve of P. inaequalis except 

 that it is inequilateral. 



Length 32, alt. 30 mm. 



Type no. 2854 A. N. S. P. 



Pecten (Amusium?) correctus Pils. and John?. Plate XLV, flg. 13. 



Pecten opercularis Gabb, Trans. Amer. Philos. Soc, xv, 1873, p. 256. 

 Pecten correctus Pils. and Johns. Proc. A. N. S. Phila. 1917, p. 194. 



Pecten ischnon Pils. and Jolms. Plate XLIV, flgs. 7, 8 (type). 9. 



Proc. A. N. S. Phila. 1917, p. 194. 



The concentric lineolation appears to be confined to the more 

 convex valve. 



Amusium papyraceum Gabb Plate XLIII, figs. S, 9. 



Pleuromctia papyracea Gabb, Trans. Amer. Philos. Soc, xv, 1873, p. 257. 



Smooth, with unsculptured beaks. The flatter valve is gently 

 convex in the middle, with a broad, shallow concavity on each side. 

 The type measures: Alt. 52, length 54 mm. 



Type no. 2864 A. N. S. P. 



SPONDYLIDAE. 



Spondylus bostrychites Guppy. 



Spondylus bifrons Sowerby, Q. J. Geol. Soc, vi, p. 53. Not of Goldfuss, 



1835. 

 Spondylus bostrychites Guppy, Proc Sci. Soc, Trinidad 1867, p. 176. Gabb, 



Trans. Amer. Philos. Soc, xv, p. 257. Dall, Trans. Wagn. Inst., iii, p. 7.58; 



Bull. 90, U. S. N. M. p. 124. 



Abundant, and in fine preservation. 



Spondylus gumanomocon Brown and Pilsbry. Plate XLIII, flg?. 4, 5. 



Spondylus americanus Lam., Gabb, Trans. Amer. Philos. Soc, xv, p. 257. 

 Spondylus gumanomocon Brown and Pilsbry, Proc A. N. S. Phila., 1912, p. 

 514, footnote 4. 



Type no. 2869 A. N. S. P. 



A ponderous, very large species. The figures are much reduced. 



Plica.tula gibbosa Lamarck (variety). 



Plicatula cristata Lam., Gabb, Trans. Amer. Philos. Soc, xv, 1873, p. 257. 

 The single perfect specimen reported by Gabb appears to be 

 identical with this common recent species, except that in places 

 fine radial striation or crinkling may be seen under the lens. No 

 color markings are preserved. 



DIMYACIDAE. 



Dimya grandis Dall. 



Dimya grandis Dall, Proc U. S. Nat. Mus., xix, p. 328, with var. divaricala; 

 Trans. Wagn. Inst., iii, p. 764, pi. 35, fig. 8. 



Three valves of the typical form and two of var. divaricata were 

 found among unassorted oyster valves. 



