240 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 



this stronger rib is not the first below the carina, but is preceded by a 

 number of very fine striae, which are easily overlooked, and, indeed, in 

 some parts of our specimen there seems to be a smooth space in their 

 place. 



V. Ihering regards his specimen as a variety of P. discors. But, as has 

 been demonstrated above, his P. discors is really the P. subcequalis of 

 Sowerby, and, further, according to our specimens, there are other differ- 

 ences between both, that make it advisable to separate P. unifascialis from 

 P. subcequalis as a distinct species. The chief differences are : ( i ) The 

 existence of only one spiral rib below the carina. (2) The position of the 

 tuberculiform carina on the upper whorls, which, in the present species, is 

 considerably below the middle, nearer to the lower suture, which gives to 

 the whole shell a different appearance. (3) The number of tubercles on 

 the carina, which is, in P. unifascialis, about 20 in the last whorl, against 

 only 12 in P. subcequalis. 



Record of specimens : Mouth of Santa Cruz River, i sp. 



Distribution: Jegua quemada, Suprapatagonian beds (v. Ih.). 



Gen. GENOTA Ad. 

 167. GENOTA CUEVENSIS v. Ihering. 



PI. XXXVII, Fig. 2. 



1897 G- c - v - Ihering, in: Rev. Mus. Paul., v. 2, p. 313, pi. 3, f. 10. 



Shell subfusiform, biconical. Whorls seven, in the upper part concave, 

 with longitudinal ribs and spiral cords. Last whorl large, higher than the 

 spire. Longitudinal ribs about 12-16, terminating in small nodes above, 

 these nodes forming an angulation on the last whorl ; on the upper whorls 

 the nodes are close to the lower suture. Spiral cords unequal on the 

 lower part of the last whorl (below the angulation), the larger ones are 

 slightly nodulose, the nodes situated at the points of crossing with the 

 longitudinal ribs. Mouth narrow, elongate, canal short, slightly recurved. 

 Sinus of outer lip very slight, situated on the concave part of the whorl, 

 near the suture. 



Measurements: Height, 16 mm; diameter, 8 mm (complete individ- 

 ual). Height, 22 mm; diameter, 10 mm (apex gone). V. Ihering gives : 

 Height, 32; diameter, 14 mm. 



