298 C. T. Trechmann — Cretaceous Mollusca 



recently shown that the fauna here is distinct from the usual 

 Cretaceous such as occurs at Selwyn Rapids, and that a shell which 

 occurs here and was formerly supposed to be Conchothyra parasitica 

 is really a new species of Pugnellus. Neither Ammonites nor 

 Beleninites have yet been found in this bed. Marshall has recently 

 published 1 a provisional list of fifty-two species of Mollusca from this 

 locality which seems to include a considerable number of Tertiary 

 Oamaru forms and even some recent species. He is at present 

 investigating this fauna more closely. I made a faiidy large 

 collection one day at this locality, but I await Professor Marshall's 

 work before reporting on them. 



Paljeontologv. 



Trigonia cf. Hanetiana, d'Orb. (PI. XXI, Pig. 5.) 



Voyage dans l'Amerique Paleontologie, 1842, p. 127, pi. xii, figs. 14-16. 

 Philippi, Die quataren und tert. Versteinerungen Chiles, 1887, p. 199, 



pi. xlii, figs. 1-3. 

 Steinmann, ' ' Die Gastropoden u. Bivalven der Quiriquina-Schichten ' ' : 



N.J. fur Min., Beilage Bd. x, p. 101, pi. vii, figs. 8, 9, 1895. 

 Hector, Catalogue Ind. and Col. Exhibition, 1886, p. 64, fig. 5, Trigonia 

 sulcata. 



The only other shell I saw in the Conchothyra bed in the 

 Waimakariri Gorge was a Trigonia, which occurred as single valves 

 in a friable and fragmentary condition. I collected the pieces of one 

 and succeeded in joining them together. It is undoubtedly the 

 shell that Hector illustrates without any description under the name 

 Trigonia sulcata. The curious double sculpture on the anterior part 

 of the shell makes this quite certain. Steinmann notices Hector's 

 figure, and compares it with T Hanetiana from Quinquina, in Chili, 

 and remarks " that of all known forms of Trigonia the only one 

 which compares Avith T. Hanetiana is one illustrated by Hector 

 under the name T. sulcata from the lower (sic) Cretaceous of New 

 Zealand. Both forms are obviously very closely related and represent 

 a genuine Pacific form, for which it would be best to institute 

 a special group ". He goes on to say that it does not fall well into 

 any of Lycett's Trigonia groups. 



My specimen is a right valve, and unfortunately lacks the hinder 

 part, but enough remains to give a fair description of it. The beak 

 is rather anterior and the shell considerably elongated behind. Tbe 

 ridge which passes from the beak to the hinder part is bluntly 

 angular, the sides making nearly a right angle with one another, and 

 in front there is a wide shallow groove almost devoid of sculpture. 

 Between this and the rounded anterior margin the surface is 

 ornamented with broad and shallow concentric growth grooves which 

 are crossed obliquely by a series of about six broad and low ridges, 

 which are arranged parallel to the main posterior ridge and gradually 

 diverge and increase in size as they pass from the upper anterior part 

 of the shell backwards to the lower margin. Where they are 

 strongest they tend to obliterate the concentric grooves of growth. 

 The teeth cannot be seen. Height 50 mm. 



1 " Belations between Cretaceous and Tertiary Eocks " : Trans. N.Z. Inst., 

 vol. xlviii (new issue), p. 114, 1915. 



