The Invertebrate Fauna of the Uitenhage Series. 125 



TRIGONIA TATEI Neumayr. 



1867. Trigonia cassiope E. Tate, Quart. Journ. Geol. Soc., vol. xxiii., 



p. 158. 

 1881. Trigonia tatei M. Neumayr, in E. Holub and M. Neumayr, 



Denkschr. d. k. Akad. Wiss., Math.-Nat. Cl., Band xliv., 



p. 275, pi. ii., fig. 3. 



Occurrence. A very imperfect and ill-preserved fragment of a 

 costate Trigonia occurs in hard limestone with Pleuromya baini 

 from Grass Ridge, three miles east-north-east of Uitenhage (335). 

 In all probability this represents T. tatei. 



Remarks. Although no complete or satisfactorily determinable 

 specimens of this well -characterised form are included in the collec- 

 tion under examination, it may be useful to draw attention to one 

 or two points of interest in reference to the occurrence of this shell, 

 the only member of the section Costatae hitherto found in the 

 Uitenhage beds. In 1877, Lycett * cast doubt upon the correctness 

 of Tate's identification of this South African form with the European 

 Oolitic shells named T. cassiope by d'Orbigny,f and Neumayr sub- 

 sequently saw the necessity of applying a new name. T. tatei 

 certainly cannot be united with any other known costate form, and 

 although the general outline and nature of the ribbed flank has a 

 close parallel in several familiar European Costatae, yet the narrow 

 area and elongated escutcheon, the delicate and little-prominent 

 carinae and inter-carinal ridges, and the relatively very delicate 

 beaded ornamentation of area and escutcheon, are very distinctive 

 features. 



Two specimens preserved in the collection of the Geological 

 Society of London are labelled " Zwartkop Eiver " (H. Longlands) 

 and " McLoughlin's Best" (Major Kocke) respectively, and the 

 former specimen appears to have been the one upon which Tate's 

 identification was based. The length is relatively great compared 

 with the height ; the cardinal margin is elongated, while the siphonal 

 margin is short. The area is slightly convex in form, without a 

 marked median carina or groove ; the escutcheon is large, and 

 ornamented by raised lines of granules running parallel to the 

 ridges of the area. There are about 18 ribs on the flank of 

 the larger specimen. The elongated form, the very delicate carinse, 

 the fine intercarinal sculpture, the convex area, and the elongated 

 granular escutcheon, are all characters which at once recall the 



* Lycett (3), p. 172. f d'Orbigny (4), vol i., p. 308. 



