30 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 



The specific name is derived from the Rio Tarde, near which the fossil 

 was found. 



Locality and position. From the Ammonite (Belgrano) beds at mouth 

 of cafton four miles east of Lake Pueyrrydon. 



TUBULOSTIUM PUPOIDES Sp. nOV. 



Shell of medium size, dextral, subglobose, or very stout pupiform, 

 with a very broad, rounded apex, umbilicated, with the umbilicus broader 

 in the young than in the adult, when it is almost closed ; whorls four or 

 five, slightly flattened on the sides, convex above and below, the last one 

 much contracted and produced in a short free tube near the circular aper- 

 ture ; surface marked by obscure irregular transverse wrinkles and by a 

 small spiral furrow near the middle of the whorl. On the best preserved 

 specimen the sutures are linear and inconspicuous, but two other speci- 

 mens, believed to belong to the same species that have lost the outer layer 

 of shell, show rounded whorls and deep sutures. 



The type measures 10 mm. in height and 9 mm. in greatest breadth. 

 The contracted aperture is 3 mm. in diameter. 



This species was overlooked until after the drawings were all made and 

 arranged in plates and for that reason a figure is not given. It is evi- 

 dently congeneric with Tubulostimn callosmn Stoliczka, 1 from which it 

 differs in its more nearly pupoid form, in its rounded base and in the ab- 

 sence of the "external callosity." Stoliczka refers the genus to the Ver- 

 metidae. Somewhat similar forms have been described as Annelids, and 

 one such, Serpula phillipsi Roemer, is mentioned by Behrendsen 2 as oc- 

 curring in the Aptian of Portzuelo de Carqueque, Argentine Republic. In 

 fact the determination of the Aptian or Gault at that place seems to be based 

 on the presence of that species. As figured by Phillips 3 under the name 

 Vermicularia sowerbii it is somewhat larger than our species, its apex is more 

 conical, the umbilicus is broader, and the last whorl is not narrowed and 

 produced in a free tube. These differences are certainly sufficient to sep- 

 erate the Patagonian form from Roemer' s species, and yet the general re- 

 semblance is close enough to suggest a possibility that Behrendsen may 

 have had the Patagonian species. He states, however, that he had nu- 



1 Cretaceous Fauna of S. India, Gastropoda, p. 241, pi. 18, figs. 26-32. 

 2 Zcitschr. Deutsch. Geol. Gesellsch., Bd. 43, p. 418, 1891. 

 3 Geology of Yorkshire, pi. 2, fig. 29. 



