256 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 



Length of carapace: 66 mm; width, 91 mm. 



Remarks : There is not the slightest doubt that Cancer patagonicus is 

 identical with Portunus peruvianus of d'Orbigny, which has been placed 

 by A. Milne-Edwards in the genus Carcinus. Our specimens agree com- 

 pletely with the description given by Philippi and A. Milne-Edwards, 

 with the exception that the front possesses distinctly four, not three teeth. 



The systematic position of this crab is very doubtful. A. Milne- 

 Edwards places it with the genus Carcinus Leach (= Carcinides Rathbun, 

 Proc. Biol. Soc. Washington, v. n, 1897, p. 164), and, indeed, there is 

 some general resemblance to Carcinides mcenas of the European seas; 

 but the fact that the front has four teeth is strongly opposed to this classi- 

 fication. In my opinion there is a very striking resemblance to the living 

 genus Geryon (see for comparison the figure of G. quinquedens Smith, in : 

 Trans. Connect. Acad., v. 5, 1897, pi. 9, f. i). 



Geryon, however, is no Cyclometope, but a Catometope, and belongs to 

 the most primitive group of the latter division, which is intimately connected 

 with the former. But since the position of the male sexual opening has 

 not been ascertained in our fossil, this opinion remains to be confirmed, 

 although the writer personally is strongly in favor of it. 



Record of specimens : Mouth of Santa Cruz River, 4 sp. ; Mt. of Obser- 

 vation, lower horizon, 2 sp.; San Julian, Darwin Station, 2 dactylopodites 

 of first pereiopod ; Lake Pueyrredon, 600' above base, i sp. 



Distribution: The provenience of d'Orbigny's and Milne-Edwards' speci- 

 men is unknown. Philippi records his species from Monte Leon, Pata- 

 gonia (near the mouth of the Santa Cruz River). 



Note: Other species of Decapods existed in the Patagonian beds, as is 

 shown by a number of fragments of chelae from San Julian, Darwin Sta- 

 tion, which are different from those of G. perumamis. But it is impossible 

 to classify them. 



LIST OF FOSSILS DESCRIBED. 



MAGELLANIAN BEDS. 



1. Ostrea torresi Phil. 6. .Meretrix (?) pseudocrassa~(Ortm.). 



2. Cardita elegantoides Ortm. 7. Dosinia magellanica Ortm. 



3. Lucina neglecta Ortm. 8. Lutraria (?) undatoides Ortm. 



4. Venus difficilis Ortm. 9. Panopea ibari Phil. 



5. Venus arenosa Ortm. 10. Panopea subsymmetrica (Ortm.). 



