56 
RECORDS OF THE AUSTRALIAN MUSEUM. 
Jackson Pholas with the figures illustrating the former (Thesaurus 
Conchyliorum, Vol. ii., pi. ciii., ff. 12, 13, 14).* * * § Having no 
examples of the New Zealand species at my disposal, I am con- 
strained to base my remarks on these engravings, which, from 
their finish, should be faithful representations. Sowerby’s mistake 
in supposing the species to be an undescribed one, implies that 
he had Gray’s types before him ; while both Philippi’s diagnosis 
of P. antipodum\ and Gray’s description answer well to these 
drawings and also leave no room for doubt that the specimens 
were actually obtained in New Zealand. 
Viewed from the ventral side the difference is most apparent, 
the gape extending a third further along the ventral margin, and 
being much wider anteriorly in Sowerby’s figure than in the local 
species ; P. similis may be likened to a cylinder cut obliquely at 
an angle of 30° and P. obturamenium to one cut at an angle of 
45° Dorsally the profile of the New Zealand form appears to be 
more swollen and to taper more sharply at the anterior extremity 
than does the Australian. The spinose ridges would seem to be more 
feebly developed, and the size to be smaller in the local species ; 
but, without more material for comparison, the writer would not 
attach specific importance to such characters. The Sydney shells, 
having been procured from sandstone rock, may reasonably be 
supposed to be smaller and smoother than if their burrows had 
been drilled in softer substances. 
The next ally of our species seems to be P. manilensis , Philippi, J 
next to that the British P . parvus, Pennant, and least of the 
three the New Zealand P. similis. The unfigured Papuan P. 
beccarii , Tap. Can.§, probably is akin. 
These five appear to represent a small and natural group, among 
which the Australian species is clearly distinguishable by the 
more anterior position of the beaks and by the less posterior 
extension of the gape. 
This species may be characterised as follows : — 
Pholas obturamentum, sp. nov . 
Shell somewhat tongue-shaped, evenly tapering from the beaks 
to the posterior extremity, rounded posteriorly, dorsal and ventral 
margins straight, gibbous ventro-anteriorly, the closed valves in- 
cluding a heart-shaped space rather longer than wide ; valves in 
* Except Philippi's Abbild. Beschr. Conch., Vol. iii., Pholas, pi. i., f. 3., 
the other published figures, viz.. Conch. Icon., Vol. xviii., Pholas , pi. iii., 
f. 10, and Conch. Cab. (2) Vol. xi., pt. xx., pi. vi., f. 3, are mere copies, 
the latter a bad one, of Sowerby’s f. 12. 
f Zeits. ivial. iv., 1817, p. 71, &c. 
X Thes. Conch, pi. ciii., £f. 17, 18. 
§ Ann. Mus. Civ. Genova, vii., p. 1032. 
