362 Prof. J. Orton on the Geological 



age. This Punta, the saddle which divides the rivers Cachi- 

 yacu and Mayo, continues northward ; and through its limestone 

 strata the Maranon has cut the Pongo de Manseriche. The 

 limestone at the Pongo yielded me a Protocardia, a linguiform 

 Ostrea, and an Exogyra of Cretaceous type. All the Pongos 

 on the Upper Maranon are made through limestone mountains. 

 The Punta de Schalca is also a prolongation of the calcareous 

 range which crosses the Huallaga at the Pongo de Aguirre. 

 It is probable therefore that this western wall at the head of 

 the Amazons valley is of Cretaceous age. 



The Cerro de lcuto is flanked on the east with saliferous 

 red sandstone. It contains the valuable salt-mines of Cachi- 

 puerto, on the Cachiyacu ; and without doubt the salt-hills of 

 Chasuta and Pilluana on the Huallaga belong to the same 

 formation, as also the gypsum-beds in the elevated ridge sepa- 

 rating the Huallaga from the Ucayali. The Cerro de Sal, 

 further south, near the head of the Pachitea, may likewise be 

 contemporaneous*. The lcuto rock is unfossiliferous, and I 

 could not find its relation to the Schalca limestone. The 

 great Moyobamba valley, enclosed between the Schalca and 

 Piscoguanuna ranges, is lined with friable shales of divers 

 colours (red, yellow, purple, blue, and black), with overlying 

 soft white sandstone. Drs. Raimondi and Spruce refer this 

 to the Triassic. Near Tarapoto, where the shales contain 

 Ammonites of immense size, there are jointed columns of trap- 

 rock and cliffs of white salt. 



In crossing the Andes in the latitude of Lake Titicaca east- 

 ward, we first find Oolitic formations largely covered with in- 

 trusive rocks. After passing the summit of the coast Cordillera 



the Kelloway division of that formation : he. Conrpuerta, near Lake 

 Titicaca, fifty miles north-west of Puno, altitude of 13,500 feet. Sfephano- 

 ceras mucrocephalum, Waagen : the identity of this, as well as the former, 

 with European species cannot be doubted ; it indicates the same division 

 of the Jura : he. Caracolis, near Lake Titicaca. It is probable that the 

 whole series of Jurassic rocks exist in Peru and Bolivia. 



"Cretaceous Ammonites. — The remarks upon the specimens in this 

 division are interesting 1 simply because they have furnished me the means 

 of establishing a new genus to include the forms which have hitherto 

 been regarded as Cretaceous Ceratites. This genus I have called Buchi- 

 ceras, in honour of the great German geologist Leopold von Buch. It 

 includes the following species : — B. bihbatum, Hyatt, n. sp., he. Punta de 

 Schalca, Northern Peru ; this would be generally supposed to be identical 

 with the Amm. syriacus, Von Buch, but the comparison of authentic spe- 

 cimens shows specific differences ; B. serratum, Hyatt, n. sp., he. Cachi- 

 yacu, Northern Peru, doubtless washed down from the Punta de 

 Schalca." 



* The gorge of Tunkini on the Upper Ucayali is described by Castelnau 

 as "freestone."' 



