.304 Chapman and Gabriel: 



:]. Aicoinpanyinf; the typical (t. maccoiji at Table Cape (ex At- 

 kinson coll. in the National Museum, Melhouine). are shells in 

 every way ci.uiparable with the form approaching G. laticosfatus, 

 Q. and (i.. and figured by McCoy from Bird Rock. This we refer 

 to form b (antea). 



4. The several mutations of the above species sliow it to com- 

 mence in the Balcombian as a moderate-sized shell with about 29 

 riblets, persisting into the Janjukian. Side by side with this form 

 the mutation b springs up, but disappears before the Kalimnan. 



5. The Kalimnan variant (form c) resembles tlie Balcombian 

 (small var.) species, btit is even smaller, and retains the Janjukian 

 character of form b in having a more deeply concave umbonal 

 cavity. (PI. xxiv. fig. 5.) Its archaic character is seen in the num- 

 ber of its riblets, 26-30 (F.C. coll. in Nat. Mus. Melb. from Mac- 

 Donald's, Muddy Creek). 



6. The Bird Rock and Table Cape variant, form b, is ilearly 

 the Janjukian ancestor of G. Inticostafiig, Q. and (i. {furnia rem), 

 which later on inhabited the Pliocene sea at Wanganui. and is now^ 

 confined to the area round New Zealand and the Chatham Islands. 

 From G. laticosiatus, Q. and G.. the form b of Table Cape and 

 Bird Rock differs in having a longer shell (ant. -post.) and a more 

 finely striated ligamental area. (PI. xxv. fig. 6.) 



7. In the Kalimnan series G. fiKicco/// merges into G. subfngo- 

 nalis, Tate,2 by the truncation of the anterior cardinal angle. 



All the specimens of G. maccoyi from the Mallee bores belong to 

 form a, having fewer riblets and moderate dimensions. 



Distrihution.— Bore 5, 162-163 feet; 175-189 feet. Bore 6, 158- 

 161 feet. Bore 8, 165-180 feet; 199-204 feet; 204-210 feet. Bore 

 5, 254-256 feet. 



Fain. TKKIONIIDAE. 

 Genus TRIGONIA. Bruguieie. 

 Trigonia lamarcki, Gray. (PI. XXV., Figs. 7-9). 

 Trigoiiia lamarckii. Gray, 1838. Ann. and Mag. Nat. Hist., 

 vol. I., p. 482, Reeve, 18(;o. (^.nch. Icon. vol. xii. pi. 

 i.. figs \<i-v. T. Woods, ISSS. (Journ. Hoy. S.>c. N.S. 

 Wales, vol. xxii.), p. 163, pi. x. figs. 16. 17: pi. xiv. 

 figs. 25, 26. 



1. Typicaiexami)le8ofy.Zaf,co«fa^(k-,y. and G. sp., from the Wauiraiuii I.eds of N. Zealand, 

 .are in the Melbourne National Museum. 



•2. Trans. R. Soc. S. Austr., vol. viii. (for lSS4-.'->), l«8(l, p. l.tT, I'l. xi., fij;s. 6«, ('. 



