PECTUNCULUS. 341 



depressions, the whole being crossed by very closely-set lineations, 

 and few ridges of growth ; umbones small ; area constricted, 

 grooved ; hinge-line very short ; teeth few in number ; inner 

 margin of the valves broadly and strongly crenulate. 



The surface ornament recalls the European Oligocene P. angusti- 

 costa, Lamarck, but the latter shell is orbicular, has a smaller 

 ligament area, and more numerous teeth. 



Dimensions. — Height 27 mm. ; length 27 mm. 



Form, and Loc. — Eocene : South Australia and Victoria. 



L. 4826. Two valves, much waterworn ; from Muddy Creek. 



Presented hy John Dennant, Esq. 



L. 9897. Several examples of the adult ; from Eiver Murray 

 cliffs. Purchased. 



Pectunculus laticoStatUS, Quoy and Gaimard. 



1834. Fectuncubts laticostatiis, Quoy and Gaimard, Voy. de I'Astrolabe, 



vol. iii. p. 466, pi. Ixxvii. figs. 4-6. 

 1875. Pectunculus laticostatus, M'Coy, Prod. Pal. Vict. dec. ii. p. 26, pi. six. 



figs. 10-14. 

 1884. Pectunculus maccoiji, Johnston, Pap. Roy. Soc. Tas. p. 199. 

 1886. Pectunculus laticostatus, Tate, Trans. Roy. Soc. South Aust. vol. viii. 



p. 137. 

 1886. Pectunculus maccoyi, Tate, id. p. 137. 

 1888. Pectunculus maccoyi, Johnston, Geol. Tasmania, p. 235, pi. xxxi. 



figs. \-\d. 

 1893. Pectunculus laticostatus, Tate and Dennant, Trans. Roy. Soc. South 



Aust. vol. xvii. pt. 1, p. 224. 



1895. Pectunculus laticostatus, Tate and Dennant, id. vol. six. pt. 1, p. 112. 



1896. Pectwiculus laticostatus, Pritchard, Proc. Roy. Soc. Vict. vol. viii. n.s. 



p. 130. 



This species is closely allied to P. sultrigonalis, but it is thinner, 

 suborbicular (instead of subtrigonal), much more depressed, and 

 has a narrow hinge-line. Comparison of authenticated specimens 

 of P. maccoxji, Johnston, with the living P. laticostatus, enables the 

 writer to state, definitely, that they are synonymous. 



JJimetisions. — Height 72 mm. ; length 74 mm. 



Form, and Loc. — Eocene, Miocene, and Pliocene : Tasmania, 

 Victoria, South Australia, and Xew Zealand. 



83998. Left valve narrower than typical specimens ; from 

 Table Cape. Purchased. 



98220. Left valve ; from Table Cape. Purchased. 



