454 Transactions. 



Has almost exactly the same form as H. gabbi, and the same general type 

 of sculpture, but the spiral lines are much more numerous and more nearly 

 of uniform size over the entire surface. While specifically distinct, it seems 

 to me certainly congeneric with H. gabbi and H. trochoidea, the latter being 

 the type of the genus Heteroterma, which Gabb described in Palaeontology 

 of California, vol. 2, p. 151, 1869. This genus seems to me to have escaped 

 mention in the manuals and text-books, and so far as I know has had no 

 authoritative treatment since the time of Gabb, who referred it to the 

 Pleurotomidae." 



Cossmann remarks on this genus (Essais de Paleoconchologie comparee, 

 4 e livraison, p. 69), " Peut-etre est ce dans ce dernier Genre (Tudicula) qu'il 

 y a lieu de placer Heteroterma Gabb qui, ainsi que j'ai indique dans le 

 3 e livraison de ces Essais ne parait pas bien classe dans la famille Pleuro- 

 tomidae. La coquille a une forme de Tudicida mais l'auteur indique 

 Texistence d'une echrancure a la suture. En definitive cette question 

 demande a etre revisee." Cossmann* also places Pyropsis Conrad in this 

 genus Tudicula. Species of Pyropsis are mentioned by Wilckens from 

 the Quiriquina beds of Chile and from south Patagonia. Wilckens lays 

 emphasis on the Cretaceous age of this genus. I am informed by Dr. 

 Stanton that Heteroterma gabbi comes from the Martinez beds, which con- 

 stitute the oldest Eocene formation of California. 



Four specimens. Type in the Otago Museum. 



Perissolax obtusa n. sp. (Plate XXXV, figs. 22, 23.) 



Small complete specimen, 17 mm. by 8 mm; another specimen, nearly 

 complete, 55 mm. by 30 mm. Shell of moderate size, with four rapidly 

 increasing whorls somewhat shouldered. Upper whorls nearly smooth, 

 though the last whorl is ornamented with rounded tubercles, about 12 to the 

 whorl. Body-whorl large, with 3 distinct carinae, each of which bears a 

 row of rounded tubercles — the upper 9, the middle 11, and the lowest 13 

 in number : those on the anterior carina are smaller than the others. Thus 

 the tubercles do not occur in distinct vertical rows, as they frequently do 

 in this genus. Suture markedly undulating. Spire with no ornamentation 

 other than the tubercles. Body-whorl with a number of spiral lines : 12 of 

 these lie between the suture and the upper row of tubercles, 13 between 

 the first two rows, and 8 lines between the second and third rows of 

 tubercles : these spiral lines are continued on the side of the anterior canal, 

 where they become larger and somewhat more oblique. Canal moderately 

 long and slightly bent inwards in the middle. 



Type in the Otago Museum. 



In the list of the Wangaloa fauna that was published last year this species 

 was classed under Euthriofusus n. sp., but as it was apparent that there 

 was an extremely close relationship between this species and Perissolax 

 brevirostris Gabb a specimen was sent to Dr. Stanton. He has been good 

 enough to examine the specimen, and has sent me the following critical 

 remarks :- — 



' This species is apparently congeneric with Perissolax brevirostris Gabb, 

 which it resembles in general form and style of sculpture ; but it is some- 

 what shorter, and differs in all details of sculpture. The spiral lines are 



* In a letter just received Cossmann says, " J'ai examine Heteroterma qui me 

 semble bien determine generiquement." 



