164 
30 
Fig. 9- Obesomanus group; variations in propor- 
tions of antennular articles in three species. Ordinate: 
length of second article divided by length of first 
article. Abets sa: number of specimens. 
attributed to A. malleodigitus there appears to 
be a bi- or even tri-modal curve which could 
indicate two or three separate species with over- 
lapping variation; however, in careful correla- 
tion with other characteristics we could find no 
related differences that could separate these 
groups. Therefore, we have interpreted this as 
a probable difference in geographically sep- 
arated populations. 
Antennal peduncle (Figs. 11, 12, and 13). 
In this appendage there is a clear differentiation 
between A. obesomanus and A. malleodigitus 
in the relative lengths of the scaphocerite and 
carpocerite when compared with the anten- 
nular articles, the scaphocerites being definitely 
shorter in the latter species; A. obesomanus and 
PACIFIC SCIENCE, Vol. XX, April 1966 
A. microstylus, similar in their carpocerites and 
scaphocerites, are differentiated by the lengths 
of the squamous portion. In A. microstylus the 
squame reaches to near the end of the third, and 
in A. obesomanus it reaches only to the middle 
of the second antennular article. 
Large chela. On this appendage emphasis has 
been made on the degree of sculpturing. In 
most specimens the chitin of the body of the 
chela is relatively soft, being stiff only where 
muscles or ligaments are attached; as a con- 
sequence the process of preservation alters the 
extent of the depressions and grooves, and no 
great significance should be attached to either 
their depth or breadth. However, all had some 
indentations, and none closely approached the 
smooth condition reported by Dana for his 
species A. obesomanus (his drawing appears 
to be of the medial face, which is smooth in 
most species of this group ) . 
Small chela (Fig. 14). This characteristic has 
been used by de Man (1911:313) as a dis- 
tinguishing characteristic in his key ("fingers 
of small chela of the male much shorter than 
palm, the proportion between the length of the 
Fig. 10. Obesomanus group; proportions of second 
antennular article in three species. Ordinate: length 
of second antennular article divided by its breadth. 
Ahcissa: number of specimens. 
