32 AXEL A. OLSSON 



Scapho'poda 



Of the classes of the Panamic Mollusca, the scaphopods with about 

 14 species are the least known (Dentalium, 11 species and Cadtdus, 3 

 species). As noted by Pilsbry and Sharp (1897), the shallow-water Scapho- 

 poda of the eastern Pacific are closely related to forms from the Antillean 

 Tertiary and Recent faunas, whereas, the offshore, deep-water species 

 belong mainly to what seems to be endemic West American, and have no 

 allies in Antillean or Oriental seas. Characteristic of the West Coast species 

 are Dentaliums of the subgenus Tesseracme, unknown by any living species 

 in the present-day West Atlantic. They were well represented there during 

 the Miocene and Pliocene periods. A Dentalium related to D. pretiosum 

 (Antalis group) is encountered in beach drift along the Santa Elena 

 Peninsula in Ecuador, Only two scaphopods are known so far from north- 

 western Peru, namely D. (Graptacme) splendidwn and Cadulus (Gadilia) 

 perpusillus; both species are also found in Ecuador. 



Amphineura 



The chiton fauna of the Panamic-Pacific Province seems relatively 

 small in the number of species, probably because of incomplete explora- 

 tion. The common large chiton along the surf line in Panama and Ecuador 

 is C. stokesi, gathered by the natives for food and bait. Other shore species 

 in Panama are Chaetopleura lurida, Ischnochiton adamsi, and the lovely 

 Tonicia crenidata. Acanthochites hirundinijormis has been obtained at 

 Manta and Santa Elena, Acanthopleura echinata, primarily a cold-water 

 species of the Peruvian Province, occurs as far north as Cabo Blanco. 



THE PERUVIAN PROVINCE 

 ITS LIMITS AND PAUNAL CHARACTERISTICS 



The Panamic-Pacific and the Peruvian faunal provinces border along 

 the northwest coast of Peru between the Gulf of Guayaquil and Punta 

 Aguja at the end of the Illescas Peninsula (about lat S° 40' S,). In this 

 region, the continent of South America projects the furthest west forming 

 a series of massive headlands separated by deep re-entrants or bays. There 

 are three of these coastal bulges, namely, Cabo Blanco-Punta Parinas 

 in the north; the smaller peninsula of Paita in the middle; and the Illescas 

 Peninsula in the south, the whole spread over a distance of about 120 

 nautical miles. The bays between these headlands, two in number (Paita 

 and Sechura) are asymetrical in shape and widely open to the north. The 

 bays of Manta and Santa Elena along the Ecuadorian Coast are similarly 

 shaped. Geologically, the headland areas are structural highs, the bays 

 between them synclinal. Cabo Blanco-Parinas bulge is underlain by Tertiary 

 rocks, while the peninsulas of Paita and Illescas by more ancient rocks, 

 the two latter, represent the deeply eroded cores of old mountain uplifts. 

 The sea lying off this portion of the Peruvian coast is the meeting ground 

 of two major oceanic currents; that of the Equatorial Counter Current 

 from the north, which after bathing the coasts of western Colombia and 



