ORTMANN : TERTIARY INVERTEBRATES. 2OJ 



Affinities: The type of ornamentation is essentially the same as in the 

 following species (T. morgam], but the external form is quite different, 

 being much broader and comparatively shorter, and less elongated. 



137. TRITONIUM MORGANI Ortmann. 



PI. XXXIII, Fig. 1 6. 

 1900 T. m. Ortmann, in: Amer. Journ. Sci., v. 10, p. 374. 



Shell subfusiform, elongated, with three varices. Whorls with fine, 

 unequal, spiral striae and large tubercles, the latter, on the last whorl, in 

 three spiral rows, those of the upper row large, about 7 between two 

 varices ; those of the middle row ( 5-6 ) small, and those of the lower 

 row (3-4) very indistinct, and indicated only by a slight spiral rib. Colu- 

 mella smooth, with a few indistinct crenulations in the lower part ( on the 

 canal). Canal comparatively long, narrow. Outer lip distinctly crenu- 

 lato-dentate within in the lower part, with an indistinct canaliform emar- 

 gination in the upper part, opposite to which, on the upper part of the 

 inner lip, there is a distinct dentiform fold. 



Height, 63 mm; diameter, 28 mm. 



Remarks: The specific name is given in honor of Mr. J. Pierpont Mor- 

 gan. 



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



Affinities: This species comes very near T. verruculosiim (Sow.) (1846, 

 p. 260, pi. 4, f. 63, and Philippi, 1887, p. 57, pi. 4, f. 10) from Navidad, 

 but it differs in the much more slender form, and more numerous tuber- 

 cles (in T. verruculosum there are only 2-4 between two varices). 



The two species of Tritonium known from Patagonia offer a dis- 

 tinctly Neogene feature. The genus is found from Eocene up to Recent 

 times, but the Eocene and Oligocene species differ considerably in sculp- 

 ture from our species, and it is in Miocene deposits where we first find 

 this type of sculpture. In external form as well as in ornamentation, T. 

 morgani as regards the number of spiral rows or tubercles on the last 

 whorl comes nearest to T. tarbellianum (Grat.) (see Hoernes, 1856, p. 

 203, pi. 20, f. 7-12), and especially to the more nodulose variety of this 

 species from the Miocene of Europe. It differs, however, in the more 

 slender form, the longer canal, and the slighter development of the spiral 

 ribs. 



