66 R. BULLEN NEWTON on 



species. Bellardi's first name, O. symmetrica, being without figure or descrip- 

 tion, is clearly not acceptable, but there is every reason for adopting the 

 later P. polymorpha which Bellardi fully described and figured but with no 

 reference to the radial markings, although his Figure n, representing a shell 

 with a greater number of ribs, has been separated by Mayer-Eymar as 

 P. bellardii. Fraas next described the shell as Terebratella pyramidarum, 

 and first detected the radial costae but wrongly ascribed them to Brachiopod 

 sculpture. P. polymorpha was afterwards changed to P. abundans by Mayer- 

 Eymar, because Bellardi's fig. 1 1 of his plate 3 represented another species 

 (P. bellardii, Mayer-Eymar). In an amended diagnosis Mayer-Eymar recog- 

 nised the radial striations entering into the sculpture of this shell. Again, 

 De Gregorio's P. bovensis from the Italian Priabonian rocks has been proved 

 by Dr. Oppenheim to be the same shell, the latter author, however, adopting 

 the specific name of pyramidarum introduced by Fraas. As there is no rule 

 of Zoological nomenclature preventing the use of Bellardi's P. polymorpha, 

 there is every reason for adopting it on the present occasion, as it claims 

 priority over all others. Another very probable synonym of the species is 

 Plicatula(?} malembaensis, described and figured by M. E. Vincent from the 

 Paleocene deposits of the Belgian Congo Territory of Africa, in which shell 

 the same contours and structures are to be observed, including even the 

 radial striations among its sculpture characters. Generally speaking, P. poly- 

 morpha need not be confused with any other species of the genus, especially 

 those of the African Tertiary deposits. It is, however, strangely like in form 

 to P. marginata of Say, 1 the type of which is in the Geological Department 

 of the British Museum (No. L. 13199), and which came from the Chesapeake 

 group of the Miocene as developed in Maryland, United States. This 

 American species exhibits important differences such as a bifurcation on the 

 posterior side of one of the costae, as well as possessing a series of minute 

 elongate, equi-distant granulations on the inner margin of the left valve 

 which fit into corresponding sockets of the opposing valve ; there are also 

 no radial striations, the shell being coarse and squamose. The African shell 

 shows similar nodulations within the valve although coarser and larger, and 

 there is no evidence of a bifid growth to any of the costae. The Nigerian 



1 An account of some of the Fossil Shells of Maryland : Jottrn. Acad. Nat. Set'., Philadelphia 

 1824, Vol. 4, part I, p. 136, pi. 9, fig. 4, and R. B. Newton, "List of Thomas Say's Types of Maryland 

 U.S.) Tertiary Mollusca in the British Museum," Geol. Mag., 1902, pp. 303-305. 



