252 PATAGONIAN EXPEDITIONS '. PALAEONTOLOGY. 



mains to be shown. The figure is a copy of Sowerby's and belongs thus 

 to B. varians. 



Record of specimens : Mt. of Observation, upper horizon, 2 sp. (var. 2) 

 (on Voluta ameghinoi} ; San Julian, Oven Point, ca. 50 sp. (all three 

 var.'s) ; San Julian, Darwin Station, 2 sp. (var. 2 and 3) ; Upper Rio 

 Chalia, 5 sp., and a large colony of ca. 40 sp. (all three var.'s) ; 30 miles 

 north of upper Rio Chalia, 7 sp. (6 forming a small colony) (var. 2 and 

 3); Shell Gap, Rio Chico, upper horizon, 8 sp. (var. i) ; Lake Pueyr- 

 redon, base of Tertiary, 13 sp. (var. I, 2 and transition to 3). 



Distribution: San Julian (Sow., Darw.). Darwin gives with a ?: East- 

 ern plain of Tierra del Fuego. Philippi gives : Ancud and Tubul, Chili 

 (Navidad beds), but he did not know the opercula. V. Ihering (1897, 

 p. 339) records B. varians from the Patagonian formation, without local- 

 ity, and B. lavis (according to Weltner) from the Suprapatagonian beds. 

 According to our material, B. Icsms is not found in these beds, but ap- 

 pears first in the Cape Fairweather beds (see below). 



Affinities: The genus Balamis is extremely rare, and even doubtful in 

 Eocene deposits (see Zittel, 1885, p. 543 and 545). It becomes more 

 abundant from the Oligocene upward. 



Darwin compares our species with B. ungniformis Sowerby from the 

 Upper Eocene and Lower Oligocene beds of England and Belgium (1854, 

 a, p. 29, pi. 2, f. 4; 1854 b, p. 296, pi. 8, f. 8). The fact that in B. va- 

 rians the parietes are sometimes perforated, brings it still closer to R. 

 itnguiformis, but in both the form of the scutum and tergum is different, 

 especially the tergum has a broader and longer spur in B. ^^ng^l^formis, 

 and, further, the basis in the latter has no pores. 



178. BALANUS cf. TRIGONUS Darwin. 



PI. XXXVIII, Fig. 4"-'. 



1854 B. t. Darwin, Mon. Cirrip. Balan., p. 223, pi. 3, f. 7. 

 1897 B- * Weltner, in: Arch. f. Naturg., v. i, p. 262. 



Parietes and basis with pores. Parietes ribbed (very rarely smooth). 

 Orifice broad, subtrigonal. Scutum thick, with from one to six longitu- 

 dinal rows of little pits (rarely wanting) ; articular ridge ending in a small 

 point below; adductor ridge short; a narrow, deep pit or cleft for the 

 lateral depressor muscle. Tergum with blunt apex and scarcely a trace 



