162 
Other species given by Couriers as being re- 
lated to A. villosus can be separated by a num- 
ber of characteristics. A. malleator Dana differs 
in the form of the rostrum and orbital hoods 
and in the large chela; A. mgimanus A. Milne- 
Edwards differs in the large chela; A. socialis 
Heller lacks the tooth on the merus of the third 
legs; and A. macrocbims Richters lacks the 
orbital teeth and differs in the form of the large 
chela. 
This species has been named in honor of 
Prince Tungi of the Kingdom of Tonga, who 
was most cooperative during the field work on 
Tongatabu. 
OBESOMANUS GROUP 
In the Obesomanus group a large number of 
species have been described based upon few 
specimens; as in other groups rather subtle dif- 
ferences in form of rostral front and chelae, and 
slight to major differences in proportions of 
articles have been used as criteria for the dif- 
ferentiation of the species. Inasmuch as it has 
become apparent in the study of our collections, 
which contain relatively large numbers of some 
species, that these species are possibly the most 
variable of all the species of Alpheus , we have 
decided to study the extent of variation in 
characteristics used as criteria to separate the 
described species. 
This paper has been chosen as the logical one 
PACIFIC SCIENCE, Vol XX, April 1966 
of the series in which to discuss this variation 
and to evaluate the validity of the Indo-P'acific 
species placed in this group. For this study all 
of the specimens in the collections available, 
those already reported, those reported in this 
paper, and those to be listed in future papers, 
were carefully examined. 
Of the numerous species attributed to this 
group we now recognize only six in our Central 
Pacific collections: A. obesomanus Dana, A. 
malleodigiius (Bate), and A . microstylus 
(Bate), all with numerous specimens, and A, 
per plexus Banner, A, chamorro Banner, and A . 
Samoa (described below) with but few speci- 
mens. In our reconsideration of the group we 
have decided that the genus Thunor is not valid 
and we have placed its species also within the 
Obesomanus group, thereby adding two more 
central Pacific species, A . idiocheles Coutiere 
and A. micros cap bis (Banner). 
In only the first three species could variation 
be studied. For these three species samples were 
compared from all parts of the range represen- 
ted. Because no significant differences were 
found from one locality to another, figures on 
their variations were combined. A total of 80 
specimens of A. obesomanus , 87 specimens of 
A. malleo digitus, and .9- specimens of A. micro - 
stylus (all of them "reasonably intact) were 
measured. To show the normal form of the 
three species, the anterior body region and the 
TABLE 2 
Differentiating Characteristics of A. villosus and A. tungii 
A. villosus A. tungii 
1. Median crest of carapace bearing tooth posterior 
to the orbital hood. 
2. Secondary teeth between orbital teeth and rostrum. 
3. Orbital hoods covered with an enmeshment of 
hairs ( "entremelees de poils”) and corneas of eyes 
"depigmentees et de couleur crayeuse,” 
4. Third leg with carpus armed with 5 movable spines 
and only slight superior distal tooth; propodus 
armed on inferior margin with over 8 pairs of 
spines; secondary unguis of dactylus heavy. 
5. Inner uropod with outer distal margin unarmed. 
1. Median crest without tooth. 
2. Secondary teeth lacking. 
3. Orbital hoods with hair light and scattered; cor- 
neas of normal pigmentation. 
4. Third leg with carpus lacking movable spines, su- 
perior distal tooth heavy; propodus with 5 pairs 
of spines; secondary unguis of dactylus slight. 
5. Inner uropod with outer distal margin bearing a 
row of movable spines. 
