Appendix to Part II. 609 



Terebratula Patagonica. — PI. II. figs. 26, 27. 



Terebratula testa ovali, lesvi, valvis fere cequaliter convexis, dwsali 

 productd, incurvd, foramine magno, ad marginem valvarumfere 

 parallelo ; deltidiis, mediocribus; area cardinali concavd, ^ longi- 

 tudinis testa ; margine antico integro. 



Slightly different from the T. variabilis of the British Crag, 

 (vide ' Min. Con.' t. 576, if. 2 to 5) to which however it is very 

 nearly related, as it is also to the T. bisinuata, Lam., of the 

 Paris basin. It may be distinguished from both by its having no 

 sinus in the anterior margin. 



San Josef and San Julian, Patagonia. 



PECTEN GEMESA.TTJS. — PI. II. fig. 24. 



Pecten testa cequivalvi, ovatd, auriculis incequalibus, costis radianti- 

 bus squamuliferis 22, geminatis ; interstitiis alternis latioribus, 

 nonnunquam costd minor e instruct a ; auricula altera magna 

 radiatim costatd. 



In general form this species resembles Pecten textorius (Schlot.) 

 Goldf. Tab. XC. f. 9, but it has very few more than half the num- 

 ber of ribs, which in the present species are disposed in pairs. The 

 P. textorius, moreover, belongs to the Lias and inferior Oolite, ac- 

 cording to Goldfuss. 



San Julian, Patagonia. 



Pecten Darwin ianus. — D'Orbig. ( Voyage, Part. Pal/ 



(PI. III. figs. 28, 29, of this work.) 



Pecten testa fere orbiculari, subcequivalvi, tenui, utrinque convexius- 

 culd; extiis Icevi, intiis costis radiantibus, per paria dispositis, 

 prope centrum minus conspicuis ; auriculis parvis. 



Like Pect. Pleuronectes, P. Japonicus, and P. obliteratus in 

 general characters, but easily distinguished from all three by the 

 circumstance of its internal radiating ribs being disposed in pairs. 

 This species has been named and described by M. d'Orbigny, but as 

 his description is very brief, owing to the condition of his speci- 

 mens, and is unaccompanied by any figure, I have thought it 

 advisable to append the above specific character. 



San Josef, Patagonia ; and St. Fe, Entre Rios. 



