Zoeal Stages and Glaucothoe of T rizopagurus magni ficus — Provenzano 
471 
scales with minute spinules. Larvae of a West 
Indian species, D. venosus (H. Milne-Ed- 
wards), have scutellations only on the rostrum 
in advanced stages and these scales are seen 
only with great difficulty, even under high 
magnification (Provenzano, unpublished data), 
but in that species there are minute tubercles 
distributed over the carapace and abdomen. 
These tubercles, much resembling those of 
Trizopagurus larvae, are more readily apparent 
in the early stages and, as development pro- 
gresses, they become less apparent, as in T. 
magni ficus. With this exception, T. magni ficus 
is the only diogenid thus far known in which 
the larvae are so obviously ornamented that at 
least in the early stages the sculpturing is suffi- 
ciently obvious that it aids in identification. 
Perhaps this sculpturing will prove to be a 
generic character, but otherwise it is not possi- 
ble yet to designate any single feature of these 
larvae of T . magnifcus as being generically 
distinctive. 
Since this is the first species in the genus 
Trizopagurus for which the larvae have been 
studied, it is not possible to compare these 
presently described stages with congeneric lar- 
vae from other parts of the world nor to point 
out which features may be reliable as specific 
versus generic characters. Moreover, since T. 
magnifcus is the first species of Diogenidae of 
the tropical eastern Pacific for which a descrip- 
tion of the larval stages is now available, it is 
not possible to offer a list of characters by 
which larvae of this species can be separated 
with certainty from other diogenid larvae with 
which they might occur in plankton. 
The enlargement and fusion to telson of the 
fourth telson process in the third and fourth 
zoeal stages of T. magnifcus is found in the 
two species of Calcinus which have been stud- 
ied, in Dardanus arrosor , and in the land her- 
mit crab Coenobita clypeatus. None of the three 
species of Paguristes so far studied show any 
change in this process in their zoeal stages, but 
since there are at least 25 species of Paguristes 
in the West Indian faunal region alone, and 
probably well over a hundred world-wide, this 
character may show some variation. In Cliba- 
narius and Diogenes there is fusion of this 
process, but instead of enlargement there is 
reduction, even approaching apparent absence. 
Some characters, such as the spine of the 
antennal scale, may vary in size within a par- 
ticular genus (see Dechance, 1962: Fig. 3), 
and hence may be of little value as an indicator 
of genus but may be reliable as a specific char- 
acter. The mediodorsal spine of the fifth 
abdominal somite in Trizopagurus is not known 
to occur in larvae of Clibanarius or Dardanus, 
but may be characteristic of Coenobita and of 
Calcinus, Diogenes, and at least some species of 
Paguristes, while the posteriolateral spines on 
that somite usually are found in these latter 
genera and in Dardanus as well. 
In combination, the characters which dis- 
tinguish the larvae of T. magnifcus from all 
other described diogenid larvae are : the peculiar 
surface sculpturing, the trio of large spines on 
the fifth abdominal somite (shared with sev- 
eral genera, but not with Dardanus or Cliba- 
narius ), and the absence of the posteriolateral 
carapace spines which apparently characterize 
Calcinus . 
In addition to Coenobita, Calcinus, Cliba- 
narius, and Dardanus, for which larvae have 
been described from other faunal regions, there 
are within the range of T. magnifcus other re- 
lated genera ( Cancellus , Ante ulus, Alio dar- 
danus, Isocheles, and Petrochirus ) for which 
no larvae have been described from any part 
of the world. 
The glaucothoe of T. magnifcus is typical 
of the family Diogenidae in general features. 
As opposed to glaucothoes of the Paguridae, 
those of the Diogenidae (and of the Coeno- 
bitidae) are generally symmetrical (the aber- 
rant genus Diogenes is an exception), the 
chelae being of subequal size, and the tail fan 
especially being similar in both sides. The uro- 
pods in Diogenidae and Coenobitidae have well 
developed, functional endopodites, whereas in 
Paguridae the endopodites are very much re- 
duced. 
This glaucothoe differs in many respects 
from those known from other faunal regions 
and it is reasonable to expect that these fea- 
tures will be of value in separating planktonic 
T. magnifcus glaucothoes from those of other 
hermit crabs in the eastern Pacific when the 
latter have been studied. 
With respect to described glaucothoes of 
non-pagurid hermit crabs, that of T. magnifcus 
