540 STUDIES ON AUSTRALIAN MOLLUSCA, IX., 



distinct, edge of valve not plicated, thin. Specimen drawn; 

 height 1*35, length 1-55, diameter of single valve 0-45mm. 

 Another specimen; length 1-85, height l-4mm. 



Hah. — Manly Beach, in shell sand (Miss L. Parkes), several 

 specimens. 



T 5^p e. — To be presented to the Australian Museum. 



Half of this genus have radial sculpture, half concentric. 

 From the latter the novelty is distinguished by large size and more 

 oval form. 



On the genus Cyamiomactra. 



A preliminary account of this genus was given by Felix 

 Bernard * based on material dredged by Filhol off Stewart 

 Island, New^ Zealand. The petaloid cardinal of the left valve 

 suggested to him a Mactroid relationship, but he acknowledged 

 that the genus could not be regarded as an arrested phase of the 

 Mactroid model. The untimely death of this brilliant writer 

 deprived the world of the full account of the development and 

 affinities of Cyamiomactra on- which he was then engaged. 



The next reference to the subject was by Dr. Dall, w4io 

 grouped f this genus in the Leptonacea. 



Bernard's account was rather generic than specific, and it was 

 after much difficulty that 1 detected the species in Stewart Island 

 material kindly supplied me by Mr. A. Hamilton. To facilitate 

 recognition of it the original account is now supplemented by a 

 drawing of the shell (plate xxxi., figs. 7, 8). 



Its range in New Zealand has been by Murdoch extended to 

 Whangaroa Harbour in the North Island. | 



Laying stress on the entire pallial line, and inviting comparison 

 between the hinge of C yamiornacti^a and that of Cuna, 1 would 

 suggest another relationship for this puzzling genus, and class it 

 in the family CrassatellitidcB. It also seems to me that another 

 aberrant genus Hemidonax, which has been referred to many 

 different positions in the taxonomic scale, is a kindred form, 



* Bull. Mus. Hist. Nat. 1897, p. 311, fig. 2. 



t Trans. Wagn. Inst, ill., 1900, p.lll6. 



t Trans. N.Z. Inst, xxxvii., 1904 (1905), p. 231. 



