26 
AUSTRALASIAN ANTARCTIC EXPEDITION. 
It has been shown by Mr. T. Iredale * that Modiolarca was first introduced by Gray 
as a genus name for Musculus impactus. For the species under consideration it therefore 
becomes necessary to adopt Gould’s Gaimardia. 
Among recent writers Pelseneer has emphasised the distinction from the Mytilidce 
of this family, which should now be called the Gaimardiadce. 
Kidderia macquariensis sp. nov. 
(Plate II., fig. 23, 24.) 
Shell small, solid, oblong ; dorsal and ventral margins nearly straight and parallel, 
posterior margin rounded, anterior briefly produced. Colour white to cream against 
which the orange-brown prodissoconch is sharply contrasted, sometimes brick red 
on the posterior or dorsal area. Sculpture fine and coarse growth lines, the latter 
crumpling the surface. A few faint radial threads sometimes appear about the centre 
of the valve. Surface glossy. Beaks at three-quarters of the length, incurved 
approaching. Length, 8 ; height, 4 ; depth of conjoined valves, 3-5mm. 
Mr. H. Hamilton found three, February 22nd, 1914, at Hassellborough Bay, and 
20 in April, 1912, on a sandy beach near the north end of Macquarie Island. 
This species has been accepted in New Zealand for Cyamium oblongmn Smith, but 
it does not Harmonise with the original account and shadow-picture of that shell. 
Modiolarca bicolor Martens, from New Georgia, seems to be nearly allied to, and possibly 
identical with, this new species. 
Kidderia pusilla Gould. 
(Plate II., figs. 25, 26, 27.) 
Mytilus pusillus Gould, Proc. Bost. Soc. Nat. Hist., iii., 1850, p. 345 ; Id., U.S. Expl. 
Exped., xii., 1852, p. 455, pi. xliv., fig. 585. 
Modiolarca pusilla Dali, Bull. U.S. Nat. Museum, iii., 1876, p. 47 ; Id., Smith, Phil. 
Trans. Roy. Soc.,*vol. 168, 1879, p. 191 ; Id., Mabille and Rochebrune, Miss. 
Scient. Cap Horn, 1889, Moll., p. 124 ; Id., Smith, Proc. Malac. Soc., iii., 1898, 
p. 24 ; Id., Melvill and Standen, Journ. of Conch., ix., 1898, p. 104 ; Id., 
Suter, Subantarctic Is. of N.Z., i., 1909, p. 44, and Manual N. Z. Moll., 1913, 
p. 895, pi. Iii., fig. 6. 
On the one hand I note that there are various discrepancies in size, form, and colour 
between a series from Macquarie Island and the account of Patagonian specimens given 
by Gould. On the other hand Dr. Dali has written that “ Gould’s figure does not well 
represent his typical specimens,” and Mr. E. A. Smith has recognised K. pusilla from 
Macquarie Island. 
* Iredale. — Proc. Malac. Soc., xi., 1914, p. 173. 
