M<»LI,USCA — IIEDLKY. 301 



Fiuuihj TRIGONITDyE. 



T R I Gr () N I A, lirnguiei-e. 



TRIGONIA MARGARITACEA, Lamarck, 

 Var. ACUTICOSTATA, McCoy. 



Trigonia acuticostata, McCoy, Geol. Mag., iii., 1S66, pp. 481-2, 

 f. 1. 



Trigonia laniarckii. var. retlmdala, Ten. Woods, Proc. Linn. Soc. 

 N.S.W., ii., 1878, p. 125. 



(Figs. 47, 48.) 

 Stations 13, 49. 



The classification of the recent Trigonia is a subject of dispute. 

 Several species have been proposed, but no two writers have agreed 

 on their value. A preliminary examination led von Willemoes 

 Suhm to recognise four species.* His notes are probably- 

 embodied by Smith. t The references given by the latter writer 

 are not exhaustive, and if his valuation be adojDted certain 

 references should, I think, be transferred to the credit of other 

 species. 



Tapparone Canef ri, who gave the matter considerable attention, \ 

 concludes that T. lamarckii, Gray, is a mere variety of T. mar- 

 garitacea, Lamk. 



The study Lycett bestowed on this genus gives especial weight 

 to his opinion. Though he confused the nomenclature of the 

 recent species, his meaning can be recovered from the context. 

 He considered that only two recent species, T. margaritacea, 

 Lamk., and the bizarre T. strangei, Ad., are valid. § 



Having collected Trigonia at points of this coast thousands of 

 miles apart, and after careful study of the ample collection in the 

 Australian Museum, I endorse Lycett's opinion. 



In size, shape, colour and sculpture Trigonia is quite inconstant; 

 it matches Lima in the variation of the radial ribs and of the 

 warts or spines upon them. In deeper water the shell becomes 

 more spinose, a character upon which McCoy founded his T. 

 aciiticostata. Tenison Woods bestowed another name upon this 

 form, apparently because his specimens were recent and McCoy's 



* Willemoes Suhm— Chall. Rep., Narr., i., 1885, p. 462. 

 t Smith— Chall. Eep., Zool., xiii., 1885, pp. 224-5. 

 t Tapparone Canefri-Mem. Acad. Sci. Torino, xxviii., 1876, p. 241. 

 § Lycett— Monogr. Brit. Fossil Trigonia-, Palseont. Sec, xxxiii., pt. 5, 

 1879, p, 232, 



