AND MOLLUSCA FROM ANGOLA, PORTUGUESE WEST AFRICA. 575 



This form of Pholadomya is not to be confused with either P. pleuromy&formis, 

 Choffat, or P. cf. collombi, Coquand, which have been recorded by Choffat from 

 the Albian rocks of Dombe Grande in Angola.* 



Distribution. — The species is characteristic of the Cenomanian, having been 

 found in Algeria, Tunisia, Palestine (Buchiceras zone), the island of Semha near 

 Socotra, and Zululand. 



Occurrence. — The examples consist of isolated limestone casts. 



Locality. — No. 15 — Cliffs beside Catumbella Dam. 



Fam. Diceratid^;. 

 Toucasia sp. (PI. I, fig. 17.) 



Remarks. — The specimen consists of a badly preserved internal cast in a hard 

 calcareous sandstone, which appears to represent a form rather similar to that 

 figured by Orbigny t as Requienia {Caprotina) carantonensis from the Cenomanian 

 of France. In the chief lateral view of this specimen, which is evidently a lower 

 valve, a well-arched umbonal region is observed with remains of a secondary 

 umbonal body beneath it possessing a strong inward curvature at the nucleus, 

 while the opposing lateral surface is much too obscure for definition ; the valve 

 throughout is regularly compressed and of moderate width ; no indication exists 

 of the upper valve. 



Dimensions. — 



Length ...... 55 mm. 



Depth . . . . . . 25 ,, 



Width (dorsal) . . . . • . 32 „ 



The occurrence of similar fossils in the Cenomanian-Turonian rocks of Dombe 

 Grande, Angola, has already been referred to by Choffat j under the name Requienia, 

 but without description or figure, as forming part of the fauna found in the 

 " calcaires coralliens blancs." 



It should be mentioned also that the generic name Toucasia was founded by 

 Munier-Chalmas § on Matheron's type of Requienia carinata from the Aptian 

 rocks of France, 1 1 a species related to the well-known British fossil Dicer as lonsdalii 

 of J. de C. Sowerby, from beds of the same horizon,1F and which was subsequently 

 recognised as occurring in the Urgo-Aptian beds of Algeria by Coquand, under the 

 genus Toucasia.** There seems to be little doubt that Dr Gregory's specimen, 

 which resembles those species, may be regarded as belonging to this genus. 



* Mem. Soc. Phys. Hist. Nat. Geneve, 1888, vol. xxx, No. 2, pi. iv, fig. 12, and pi. v, figs. 1-3, pp. 83, 84. 

 t Pal. Francaise : Terr. Cre'taces, 1850, vol. iv, pi. 592, fig. 3, p. 259. 



\ Mem. Soc. Phys. Hist. Nat. Geneve, 1888, vol. xxx, No. 2, p. 25 ; Contrib. Geol. Colonies Portugaises Afrique, 

 1905, part 2, p. 59. § Journ. Conchyl., 1873, vol. xxi, p. 74. 



|| Gat. Foss. Bouches-durRMne, 1842, pi. ii, figs. 1-5, p. 104. 

 IT Trans. Geol. Soc. London, 1836, ser. 2, vol. iv, pi. xiii, fig. 4, p. 338. 

 ** Etndes Supple'm. Paleontologie Alge'rienne, 1880, p. 191. ■ 



