CRICK: ON AMMONITES ROBUSTUS, BLFD. 293 
middle of the lateral area instead of almost close to the umbilicus, 
and in having smaller and closer-set nodes at the margin of the 
periphery. Compared with J. (@.) Stracheyi, the difference in the 
form of the aperture of the shell, or transverse section of the body- 
chamber, is, judging from the recent Wautilus, such as might indicate 
merely a sexual difference between that species and the present one ;* 
but we are led to think that such is not the case, because the difference 
in the form of the transverse section of the whorl is shown even in 
the younger whorls, and this difference, we think, would, if merely 
sexual, not be apparent in the young shell,’ and in fact would not 
be well marked until the animal had arrived at maturity.® 
2. Juvavires (GriESBACHITES) STRACHEYI, sp. nov. 
1865. Ammonites robustus (pars), H. F. Blanford: in J. W. Salter & 
H. F. Blanford, Paleeont. Niti, p. 85. 
Shell discoidal, involute, somewhat inflated; greatest thickness 
almost close to the umbilical margin, about one-half of the diameter 
of the shell; height of outer whorl about five-ninths of the diameter 
of the shell. Whorls six or seven; inclusion nearly complete ; 
umbilicus about one-tenth of the diameter of the shell in width, 
deep, with subangular margin and steep sides. Whorl oval in 
transverse section, somewhat higher than wide; indented to nearly 
one-half of its height by the preceding whorl; periphery broadly 
convex, somewhat flattened, fairly well-defined by a row of 
tubercles on each side; sides feebly convex, sloping away from the 
umbilical margin; inner area narrow, convex, almost perpendicular 
to the plane of symmetry of the shell. Body-chamber occupying 
at least one-half of the last whorl; aperture not seen. Chambers not 
seen ; septal suture imperfectly known. ‘Test with narrow, prominent, 
rounded ribs, which usually bifurcate at about the middle of the 
lateral area, one branch or sometimes both branches again bifurcating 
near the margin of the periphery, the latter point of bifurcation being 
sometimes marked by a longitudinally elongated node, there being on 
the last half of the outer whorl eight of these nodes on each margin 
of the periphery ; nodes probably not confined to the body-chamber ; * 
ribs not passing on to the inner area of the whorl, and all interrupted 
for a short distance on the median portion of the periphery. 
This species is represented by only one example. This is the 
largest of the examples of Ammonites robustus, the dimensions of 
which are given by Blanford (op. cit., p. 85). The portion of the 
1 See figures by Dr. A. Willey, Nat. Sci., vol. vi (1895), p. 411; also Dr. A. Willey’s 
“* Zoological Results,’’ pt. vi (1902), p. 742. 
_? Dr. Willey states that it is impossible to distinguish the sexes in young shells of 
the living Nautilus. Nat. Sci., vol. vi (June, 1895), p. 412. 
3 According to Dr. Willey’s observations, propagation takes place in the recent 
Nautilus only after the last septum has been formed. A. Willey’s ‘‘ Zoological 
Results,’’ pt. vi (1902), p. 746. 
4 Since the nodes are quite prominent at the commencement of the body-chamber, 
one is led to think that they existed also on at least a portion of the septate part 
of the shell. 
