4 
Prof. P. Owen on the Anatomy 
These are faintly indicated in the magnified view of the 
mantle (PL I. fig. 2) ; but the reticular character is more 
strongly marked in Spirula reticulata , besides being associated 
with formal characters described and illustrated in the mono¬ 
graph of 1848. 
The thin semitransparent epiderm is continued beyond the 
muscular stratum from the borders of the dorsal interspace of 
the terminal lobes for about 9 millims. upon the shell, the rest 
of which is covered by the extremely thin and minutely 
granular periostracum. The same modification of the mantle 
occurs at the ventral interspace of the lobes ; but it is continued 
to a less extent, the thin corium of the mantle terminating 
by a well-defined margin from which the epiderm is con¬ 
tinued. The production of this skin upon the shell regains 
the thick fleshy border of the terminal lobes of the mantle at 
the posterior end of the interspace, which is filled up by the 
soft disk (a h) and the fin-rudiments (a c). 
The integument of the head is smooth ; it was coloured by 
minute points of brownish pigment; it is so thin around the 
eye as to permit the black pigment of the choroid to appear 
through. The original coloration of the mantle had been lost 
by long immersion in spirit. About the middle of the dorsal 
aspect were two narrow oblong marks (PI. I. fig. 1, m). 
The inner surface of the mantle, a little behind each of the 
ventral angular processes, presents a linear longitudinal pro¬ 
minence of almost cartilaginous hardness, for the cavities at 
the base of the funnel. 
This (PI. I. figs. 1, 4, PI. III. fig. 1, i) is a conical tube, 
with entire parietes ; the apical outlet unusually small, clue 
probably to strong contraction, but defended by a corre¬ 
spondingly small semicircular valve. At the sides of the 
expanded base of the funnel were the cartilaginous cavities 
(PI. I. fig. 4, o; PI. II. fig. 3, o) articulating with the pallial 
prominences. 
The head of the Spirula is defined by a feeble linear con¬ 
striction from the soft and broad valvular folds (PI. I. fig. 4, h) 
continued therefrom and from the base of the funnel, one on 
each side, to meet and blend at the dorsal aspect of the neck. 
Here the valve, which, from its functional relation to the 
mantle-cavity, maybe termed “pallial,” is impressed by a 
triangular shallow pit with a slightly raised border (fig. 4, k), 
the base turned forwards and the apex prolonged backwards. 
The antero-posterior extent of the valve, which terminates 
backward in a thin free border, is 4 millims.; it is shorter 
posteriorly, where it is attached to the dorsal retractors of the 
head. Just behind or beyond this border the peritoneum is 
reflected upon the lining membrane of the mantle. The finely 
