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42 CONTRIBUTION TO THE PALEONTOLOGY OF TRINIDAD. 



ward, postero-basal extremity rather narrowly rounded; postero-dorsal margin 

 very oblique, compressed, nearly straight, or sometimes a little convex in outline 

 below the middle, and slightly concave above, cardinal border short, straight, 

 compressed, and forming an angle of about 45 degrees with the longest diameter 

 of the shell; beaks terminal, rather small, nearly equal, obtusely pointed, rising 

 little above the hinge, and not much incurved. Surface ornamented by more or 

 less regular, concentric undulations, and smaller marks of growth." 



Remarks. — While in Venezuela the writer sent a box of Inoceramus specimens 

 to Dr. Stanton, of the United States Geological Survey, that had been obtained by 

 Mr. Veatch and the writer from ravines along the trail from Guanoco to the 

 little temiche hut village of Hurupu. Dr. Stanton very kindly examined the 

 material and wrote as follows: 



"The collection from near Guanoco, on the trail to Hurupu, includes a number 

 of specimens of an Inoceramus which is almost certainly the species identified 

 by Karsten as Inoceramus plicatus d'Orbigny which he reported from the valley 

 of Cumanacoa, eastern Venezuela, and from many other localities in that country. 

 He states that the species occurs at Barbacoas, Province of Trujillo, associated 

 with several species of Lower Cretaceous ammonites and on the basis of this 

 identification and association he refers the Inoceramus-be&rmg rocks of eastern 

 Venezuela to the Lower Cretaceous. Inoceramus plicatus was originally described 

 from supposed Lower Cretaceous rocks near Ibaque, Colombia. The fact should 

 be noted, however, that this species is very closely related to I. labiatus of the 

 Upper Cretaceous and the specimens in your collection can be almost exactly 

 duplicated by specimens of I. labiatus from the Benton of the Rocky Mountain 

 region." 



Later more material was obtained from the same locality and among the 

 specimens was one in shale (see figure) which resembles greatly the figures of L 

 labiatus in Dr. Stanton's report on the Colorado Formation. 11 This and Dr. 

 Stanton's comparisons incline the writer to regard the Venezuelan shell as a 

 form of this widely distributed species. 



Inoceramus labiatus is common in the Niobrara limestone of Kansas, Ne- 

 braska, Colorado, and the Upper Missouri region. It is also abundant in the Fort 

 Benton shales in the same states and in equivalent strata in Utah. New Mexico, 

 Texas, and northern Mexico. In Europe it is said to be found only in the Lower 

 Turonian and in southern India it is limited to the Ootatoor group which forms 

 the base of the Upper Cretaceous section of that region. 



This species is exceedingly common in certain layers of the Cretaceous lime- 

 stones in the vicinity of Guanoco. It occurs generally in very dark, exceedingly 

 hard, cherty limestone beds; but it is also found in the Cretaceous shales asso- 

 ciated with them. The shells vary from a characteristically deeply and evenly 

 grooved concentric sculpture to nearly smooth forms with the sculpture almost 

 obsolete. This causes them at first glance to appear as different species, but 



11 Bull. U. S. Geol. Surv., No. 106, pi. XIV, fig. 2. 



UJ 



