OP SOUTHEEN IXDIA. 443 



white, wliilc the smaller valve, exposed to light, is colored. The large develop- 

 ment of the hinge area, with the ligamental groove passing through it, and the 

 structure of the shell of Pedum, undouhtedly show greater affinities to the 

 Spondyli, than they do to the Fectines. 



A: Terquemia, Tate, 1867, (Suppl. to Woodward's Manual of Mollusca, 

 Carpeuteria, Deslongchamps, 1859, Mem. Soc., Linn., Norm., xi, p. 120 — noii 

 eadem, Gray, 185C). Valves radiately ribhed, externally lamellar, internally porcel- 

 lauous, rounded, generally somewhat irregular ; right valve larger, attached, usually 

 somewhat convex, left valve somewhat smaller and also flatter; hinge area 

 well developed in both valves, striated, with a ligamental groove passing through 

 it and slightly projecting internally, terminating with a roundish hole ; no hinge- 

 teeth ; muscular scar rounded, somewhat posteriorly placed, excentric, pallial line 

 indistinct; type, Terq. pectlniformis, E.-DesL, from the lias. Only a few other 

 Jurassic species have been made known. The classification of the genus in the 

 present place must be considered as provisional, for the shells are extremely like 

 Ostrea, but the hinge area and the ligamqjital groove appear to me to have their 

 nearest analogues among the Sponbtlid^, and the shells themselves show a great 

 similarity to Flicatula. 



List of cnETACEors species. 



1. PUcaliila asperrima, d'Orb., Pal. fraii9. terr. cret., iii, p. 679, pi. 462, figs. 1 — 4. 



2-5. — 7'. Ciirteroniana, d'Orb., (ibidem, p. 680), Bmmeii, d'Orb., (ih., p. %'i^\ ; — armaia, 

 Roem., non Goldf.), placunea,* Lam. (ibid. p. 6S2; ^= Sjiondylm strigilis, Brong.), radiola, 

 Lamck,, (ibid yi. 683; = ? pectinoides, Sow.). 



Q.—P. radiata, Goldf., Petr. Germ., ii, p. 102, pi. 107, fig. 7. 



7.— P. nodosa, Duj., Mem. Soc. Geol. Fr., 1837, ii, p. 228, pi. 15, fig. 14. 



8. — P. i)ijlata. Sow., (vide Mat. Pal. Suisse. — Foss. de la Pertlie du llbone, &c., par Pictet et 

 Renevier, 1858, p. 137 ; = P. sjniiosa, Mant., (Geol. of Snss., p. 26, figs. 13, 16-17; non eadeM 

 Sow., sed etidem d'Orbigny, Pal. fran9. cret., iii, p. 685; teste Coquand, Monog. Etage Apt. do 

 TEspague, p. 159). 



9.— P. onrgHis, P. and Roux, Foss. des Gres verts, 1849-53, p. 517. 



10. — P. imbricata, Koch et Dunk., Beitrsege, &e., 1837, p. 50, pi. 6, fig. 3. 



11. — P. inaquidens, Sbarpe, Quart. Journ. Geol. Soc, Loud., x, p. 197, \)\. 6, fig. 3. 



13. — P. delfoidea, Tate, Quart. Journ. Geol. Soc, Lond., xxi, p. 39, pi. 3, fig. 5. 



13. — P. axjjera, Sow., (vide Zittel in Denkscb. Akad., Wien, xxv, pt. ii, p. 120, pi. xix, 

 fig. 1, and for furtber reference p. 446). Fraas (Wiirt. Jahresb., xxiii, p. 232,) quotes tbe species 

 also from Palaestine. 



14-18. — PI. (iffiiiis, Eicbw., P. avrita, Trautscb., P.convexa, Eicbw., P. rudis, Eicbw., et 

 P. lamellosa, Eicbw., are all stated to occur iu Neocomien rocks of Russia (see Letb. ross., xme 

 livr., p. 413, et seq.). 



19. — P. Arachne, Coquand, (Mon. Jiltage Apt. de FEsiwgne, 1S65, p. 160). 



20. — Plicatula arachioidea. Desk, Mem. Soc, Linn., Norm., xi, p. 124, belongs to a peculiar 

 genus probably allied to Ci/clostreon of tbe Anomiid^h. 



21-22. — PL claihrata et delta, Deslougcb. (Mem. Soc, Linn., Normandie, xi, p. 104, pi. 17, 

 figs. 9-10 and 11-12). The second species is considered doubtfully cretaceous. 



* Coquand (Monog. Etage Aptien de I'Espagne, 1865, p. 15S), unites asperrhna, d'Orb., also witli this species. 



