241 
confined to the ridge, or the fold. Surface of the valves plain, but the fold and sinus 
are sometimes followed by one, two, three, or even four sharp, well-separated, radiating 
costas on each side, at times well marked, at others very faint and indistinct ; the inter- 
spaces between these costae are always much wider than the latter, whilst on the dorsal 
valve the fold is followed by a deep valley on each side. 
Ohs. In this species, as in the former, I have had the advantage of studying both 
good internal casts and examples with the test preserved. If Spirifera siihradiata, 
G-. B. Sby., is correctly placed in Martiniopsis, the present species will also fall into that 
genus, as their internal structure is on the same general plan. The chief points of 
interest in M. Darwinii are the very convex, dee]), and equal valves, large fold, and 
highly pinched-up sinus ; but above all the strange horizontal truncature of the umbonal 
regions of both valves, giving to the shell a square-topped or “pigeon-breasted” 
appearance, the truncated cardinal process and the fold of the dorsal valve forming, by 
their imaginary union, almost a right angle. It is this feature, with the marked 
convexity of the valves, which serves to distingiush M. Barwinii from M. suhmdiata. 
I am quite in accord with Prof. De Koninck in referring one of the shells 
figured by Professor Morris as Spirifera suhradiata, G. B. Sowerby, to the present 
species, after comparison with Morris’s type.* In justice to Prof. Morris, it must be 
borne in mind that he himself hinted at this union. Beyond this, however, I cannot go 
with this much-lamented and distinguished Palaeontologist in his interpretation of 
Spirifera Barwinii. To me all his figures of this species represent but a variety of 
Martiniopsis suhradiata, to which on a previous page I have ventured to apply the 
varietal name of Koninehi. Morris but very briefly described his S. Barwinii, and did 
Qot ostensibly figure it. In the description, my former Master refers to the equally 
convex valves, and says — “ It is a very neat shell, and presents some resemblance to one 
of the varieties of S. suhradiatus (PI. xv,, fig. Sa).” This so-called variety I take to be 
the veritable S. Barwinii of Morris, because the shell in question does not correspond 
^t all with M. suhradiata, but possesses peculiar features of its own. An examination 
of the figure quoted will show how widely it differs from any illustrations of the last- 
named species, whether those of Moi’ris or De Koninck ; and no better term could have 
eon employed in its description than that of “ neat.” Compare the elegantly alate 
Appearance of the sides possessed by “PI. xv., fig. 5a,” with the gradually compressed 
And elongated ends of the figures given by Morris of the Spirifera suhradiata. 
^fio muscular scars in the ventral valve are lingual, and in casts very prominent, 
© surface more or less hollowed or concave. In the dorsal valve the impressions are 
A most confined to the apex of the fold, and are separated by a septum. 
• . . good deal of variation occurs in the radiating costse of the exterior. In some 
individuals there is a single and indistinct rib, in others one well marked and another 
Aint, or they become more numerous as described above. 
,, ^fic internal 2 )rocesse 8 project much less into the interior of the shell than do 
ose of M. suhradiata, and, although quite as large, produce shallower imptressions in casts. 
Tatton, there appears to be a variety of this species differing from the species 
proper in having the ribs closer, rounded, and rather curved, but this is accompanied 
y the peculiarities of the cardinal process mentioned above. 
Loc. and Horizons. Coral Creek, Bowen Biver, below Sonoma Koad- 
(-®- J^ack) ; Parrot Creek, Bowen Eiver, four and a-quarter miles up (i?. L. 
) ; Richards’ Homestead, three miles south-west of Mount Britton Township, 
O 1 Middle or Marine Series of the Bowen River Coal Pield ; Tatton 
{R. L. Jack) — Gympie Beds. 
* Strzelecki’s Phya. Descrip, N. S. Wales, &c., 1845, t. 15, f. 5a. 
