502 C. T. Trechmann— 



specimens, now iix the Britisli Museum of Natural History, consist 

 of polished transverse and longitudinal sections of the upper part of 

 the shell, the latter showing the junction of the upper and lower 

 valves, and a cross section of the young shell near the apex of the 

 lower valve. They were called Barrettia monilifera in honour of 

 the discoverer. The locality where they were found was on the 

 banks of the Back River, a tributary of the Rio Grande, about 

 15 miles from the coast in Portland Parish in the north-east of the 

 island. The rock is described as a hard, grey limestone which occurs 

 in bands of a few inches to a yard in thickness, subordinate to many 

 hundreds of feet of shale which graduate up into other grey shales 

 of the Eocene, followed by white limestones of Miocene age. 



The original specimens, therefore, come from the far easterly part 

 of Jamaica, namely the Blue Mountain district, where the limestones 

 are as a rule hard and splintery, and the fossils indifferently preserved 

 and difficult to disengage from the rock. The stratigraphy in this 

 portion of the island is also much involved, though Barrett's 

 description is clear enough. I did not succeed in finding the locality, 

 which is in a wild and inaccessible area. 



J. G. Sawkins^ records a derived specimen of Barrettia as occurring, 

 together with other rolled fragments of Cretaceous limestone and 

 other Cretaceous fossils, in the conglomerates and sandstones of the 

 Carbonaceous or Black Shale series, later called by Hill the Richmond 

 Formation, near Port Maria. These beds comprise an accumulation 

 of material derived from the Cretaceous and older land, and the 

 conglomerates at Port Maria contain also fresh and slightly rolled 

 Eocene moUusca. The only specimen of Barrettia I saw in the 

 collection of the Jamaica Institute in Kingston is an apparently 

 rolled example, and may be the identical example found by Sawkins 

 in the Carbonaceous Shale. 



I have not been able to trace definite records of its occurrence in 

 Cuba, but Matthew " states that limestones at Constancia Landing 

 and Conception Estate are of j)ale buff tint, and are Hippurite 

 limestones, and contain several species of Caprinella and Caprotina. 



T. W. Vaughan ^ states that it has been collected in the province 

 of Santa Clara in Cuba. A similar fauna which may contain 

 Barrettia is also reported from Haiti. 



Its occurrence in Guatemala seems to be more definite. C. Sapper * 

 says that the greater part of northern Guatemala is made of thick 

 limestones, which often alternate with dolomite and limestone 

 breccias, and that these are for the most part certainly Cretaceous. 

 He goes on to say that the remarkable genus Barrettia, which 



^ " Reports on the Geology of Jamaica " : Memoirs of the Geological Survey, 

 London, 1869, p. 130. 



^ Canadian Naturalist, vol. vii, 1872, p. 19. 



^ Bailey Willis, " Index to the Stratigraphy of N. America " : U.S. Geological 

 Survey, Professional Paper 71, 1912, p. 643. 



* Sapper, " Grundzuge der Physikalischen Geographic von Guatemala " : 

 Peter manns Mitteilungen, Erganzungsheft 113, 1894, p. 9. 



