3oa 



Mr. J. Orton on the Evidence of 



for other localities. In February 1870 he reported a larg6 

 deposit on the south side of the Maranon, thirty miles below 

 Pebas, at Pichaua, just west of Cochaquinas *. The shells 

 were larger and more plentiful than at Pebas, but were found 

 in the same layers of red and blue clays, from six to twenty 

 feet beneath the soil. A collection (in quantity about half a 

 bushel) was received in August, and submitted to the eminent 

 ])ala3ontologist, T. A. Conrad, Esq. His paper, published in 

 the 'American Journal of Conchology,' Oct. 10, contained 

 many additional species, and corrected some mistakes into 

 which Mr. Gabb had fallen from lack of perfect specimens. 

 The following is a complete list, numbered in the order of 

 abundance. No. 1 being the most numerous f: — 



identical with the living 



is 



The Neritina, which Gabb made 

 N. pupa, proves to be a new species. The Isa^a Ortoni 

 accompanied by an immense number of small, delicate shells, 

 which Conrad considers its young. He thinks the genus is 

 related to Tricula. Liris and Dyris probably belong to the 

 Melaniidce ; and Ebora is presumed to be a freshwater genus. 

 .Of Hemisinus and Bulimus there was but one specimen each. 

 PachydonX is the most important genus, the collection fur- 

 nishing seven distinct species. Conrad makes it one of the 

 Corbulidse, though its spiral beaks are in marked contrast 

 with those of Corhula. Some of the species attained con- 



* Mr. Hauxwell writes that he has found similar shell-beds on the 

 north side of the Maranon, about a mile inland, both east and west of 

 Pebas, and also at Maucallacta. 



t The type series is now in the New- York State Geological cabinet. 



X As this name is too near Pachyodon, Conrad suggests Anisothyris. 

 It had an internal cartilage in a pit behind the tooth of the 'right valve, 

 exactly as in Corbtda ; and Meek is inclined to consider them identical. 

 The only shell observed by Darwin in the Pampean formation was Azara 

 labiata, D'Orb., one of the living Oorbulidfe. It has no spiral beak. 

 Several species of Azara (Patarnomya) live in the brackish parts of the 

 Amazon. Corbulce were abundant in the early Tertiary. See Ann. Nat. 

 Hist, for Jan. and Feb. 1871. 



