139 
The posterior end has not a continuous, smooth margin, 
but is irregular, and has a minute, triangular spine, which 
projects from it at a very slight angle on the convex ponder 
of the shell (pl. xxvi., figs. 5 and 6). This end shows signs o 
fracture, and suggests that it is not the actual commence- 
ment of the shell, but has been broken off from an earlier 
segment. 
Dredged with these are what at first sight appear to be 
another form of Cadulus, or a minute Dentaliwm, measuring 
up to four or five millimetres in length. These are curved 
like a juvenile Dentalium, and gradually increase in diameter 
and become less curved. They are evidently fractured at 
their attenuate posterior extremity, and show a minute, tri- 
angular projection from its margin on the convex side. After 
a very slight inflation near their anterior extremity they are 
constricted, and then begin to expand again into a funnel- 
shaped portion, which may measure one, two, or three milli- 
metres in length. This end is irregular in outline and evi- 
dently fractured. The funnel is clear and glassy, whereas 
the dentalium-shaped tube is like ground glass from very 
fine, crowded, transverse, milky lines. Some individuals lack 
the funnel, and end at the constriction. 
In one instance the posterior end of a Cadulus acuminatus 
has slipped into the funnel-shaped extremity of one of these 
shells, and allows a comparison to be made between them. 
In my opinion this dentalium-like shell is the juvenile stage 
of the Cudulus acuminatus. When it has grown to a certain 
length and diameter there is a trifling inflation, then it be- 
comes definitely constricted, somewhat obliquely, and thea 
begins to expand to form the mature shell. After a time 
the earlier portion becomes detached at the constriction, and 
in the fracture a tiny, projecting spine is left on the adult 
portion at the convex side, which spine is a spicule of the 
juvenile shell just where it is becoming contracted. 
If this deduction prove correct, and I have no doubt about 
it, probably all the species belonging to the group Cadulus 
dentalinus represent only immature stages of species in the C. 
acuminatus group. This will necessitate a careful re-exami- 
nation of all these forms, and a considerable revision of their 
nomenclature. 
The radula, which was difficult to get because the animals 
were dried up, shows a formula of L.1.1.1.1. Thirteen rows 
can be counted ; possibly there may be a few more in a com- 
plete ribbon. The rachidians are higher than wide, nac- 
rower at their attached end, where they are widely notched, 
with a wide, simple, flange-like cusp (pl. xxvi., figs. la, 1, le); 
the laterals are rhomboidal, much larger and stouter, espe- 

