Prionalpheus — Banner and Banner 
293 
Chace did erect a new genus Pomognathus 
(193 7: 124, fig. 5) on the basis of a species 
with an expanded third maxilliped. In Prional- 
pheus the differences lie principally in the over- 
development of the incisor process portion of 
the mandibles, with the corresponding loss of 
the palp and molar portion, and in the seem- 
ingly primitive condition of the second max- 
illiped, which, although it has coalescence of 
some of the articles, assumes a form more 
reminiscent of the maxilliped of Mysidacea than 
those of most other Decapoda. The development 
of the maxillulae differs in the two species, and 
the modification of the maxillae and of the first 
and third maxillipeds are not as striking. The 
inclusion of this genus within the family Al- 
pheidae will necessitate changes in its definition 
as given by Coutiere ("Mandibles toujours pro- 
fondement bipartites, palpe’ a deux articles. . . 
1899: 322). 
As stated above, except for the development 
of the mouth parts, this genus is most similar 
to Alpheopsis within the family. Of course, with- 
out the chelae it is difficult to decide where its 
affinities lie, but even if they were present and 
similar to those of Alpheopsis as they are ex- 
pected to be, it would still be difficult to assign 
this genus to any phylogenetic scheme for the 
family. It is generally accepted that Athanas is 
the most unmodified genus, and Alpheus and 
Synalpheus the most highly modified, on the 
basis of both the orbital hoods and development 
of the large chela; such a scheme would leave 
Alpheopsis in an intermediate position. How- 
ever, Prionalpheus , intermediate in most char- 
acteristics, is not intermediate in the modifica- 
tion of the mouth parts. 
The species of Alpheopsis available in the 
collection, including Alpheopsis equalis Cou- 
tiere, A. diaholus Banner, and A. tetrarthri Ban- 
ner, have been re-examined to determine if they 
have this modification of mouth parts. They 
do not. However, two species described by Cou- 
tiere, A. idio carpus and A. fis sipes (1908:4), 
should also be re-examined; A, idiocarpus es- 
pecially appears to be similar to P. triarticulatus. 
It is unfortunate that the specimens were so 
few in number, because a number of char- 
acteristics should be investigated more thor- 
oughly by dissection. For example, the origin 
of the peculiar tooth on the ventral side of the 
body at the base of the antennules should be 
studied; the branchial formula should be de- 
termined more carefully; the mouth parts of 
the right side should be compared to those of 
the left. With only three specimens represent- 
ing two species, it was decided to leave the 
specimens intact for future workers. 
Little can be said of the distribution of these 
species. All three were collected from the usual 
collecting site for snapping shrimp, the reef 
flat and the outer portion of the reef, in Fiji 
and Tahiti. No special niche or commensal 
association was noted for them, yet these three 
specimens were the only ones found in all of 
the collecting trips to similar habitats in these 
and other islands, collections that produced 
about eight thousand specimens. Presumably, 
these species must have special environmental 
requirements, but what the requirements may 
be we cannot say. 
The generic name is derived from the Greek, 
prionos, meaning "saw”; the gender is masculine, 
as it is in Alpheus . 
KEY TO THE SPECIES 
Carpus of second legs with three articles; only 
scattered setae on terminal article of third 
maxillipeds, these not reaching over half the 
length of that article 
Prionalpheus triarticulatus 
Carpus of second legs with four articles; terminal 
article of third maxillipeds bearing numerous 
setae equal in length to that article 
Prionalpheus species 
Prionalpheus triarticulatus sp. nov. 
Fig. 1 
TYPE AND ONLY SPECIMEN: A 107 mm. non- 
ovigerous female (3-9 mm. carapace length) 
collected in middle of reef flat on fringing reef, 
Korolevu, Vitilevu, Fiji, by senior author, 17 
March 1954 (BF-13). 
DESCRIPTION: Rostrum triangular, base de- 
marked from adjacent margin of carapace, tip 
acute, reaching to end of first antennular article, 
and bearing four short setae; dorsal surface 
with slight carina. Anterior carapace obscuring 
eyes from dorsal and lateral views, but not form 
