130 PROCEEDINGS OF THE ROYAL SOCIETY OF QUEENSLAND. 
marimus. The variation -(econsidered, for the sake of 
description, as if proceeding from scutulatus towards. 
maximus) begins in a rounding of the anterior and posterior 
median angles, thereby destroying the scutulate outline. At 
the same time the anterior portion of the shell decreases and 
the posterior tends to increase; while the growth oblique to 
the hinge line becomes more marked. 
T have refrained from attaching a definite varietal name 
to cover these forms: for, with the available information, 
and especially considering the lack of knowledge of the 
stratigraphical distribution, I cannot make up my mind 
how to place them. Two methods suggest themselves as 
being the most probable— 
(1) That these forms linking the two extremes of 
I. scutulatus and I. marimus form a variety of 
the same kind as J. concentricus var. subsulcatus? 
(which links the two forms I. concentricus and 
I. sulcatus) ; or 
(2) That the definition of J. scutulatus should be 
extended to cover forms like pl. VL., fig. 2, and 
I, maximus should similarly be enlarged to 
include forms such as pl. V., fig. 2, and pl. VL, 
fig. 3. 
Thus until further information is available I prefer to 
leave the intermediate forms in an unnamed variety inter-. 
mediate between the two species as defined above. 
INOCERAMUS PROCERUS sp. nov. 
(Ploy i fiera2) 
Sp. Chars.—Shell oval, erect, inequilateral, slightly 
inequivalve. Height much greater than length (ratio 3 : 2). 
Hinge line about half the length of shell. Umbones 
terminal, acute, very prominent. Anterior portion sharply 
truncate, posterior flattened and sub-alate. Ornamentation 
(in adult specimens) consists of widely separated concentric 
ribs only on the earlier parts of the shell, the later parts 
bemg smooth. Test very thin. Ligament pits small. 
Palhal area occupying about one-third of the internal 
surface. 
° See H. Woods: ‘‘ The evolution of Inoceramus in the Cretaceous. 
period,’’ Q.J.G.S. LXVIII., 1912, p. 4. ; 
