MICHIGAN ACADEMY OF SCIENCE. 
Ill 
Female: Similar to male; granulations on carapace less prominent. 
Annulus ventralis small, (Fig. 3 O) prominent, hemispherical, with a 
sinous longitudinal fissure; a conical tubercle (C, D) between the bases 
of the fifth walking legs which is a little larger than the annulus. 
Length, 51.7 mm . ; length of carapace, 26.0 ; rostrum to cervical groove, 
17; breadth of carapace, 13; height of carapace, 12.2. 
This species has the spine between the fifth walking legs of the female 
which Ortmann assigns as a characteristic of the subgenus Paracambarus, 
but it cannot be placed in that group on account of the characteristics 
of the male (i. e., the p resen ce of hooks on the third walking legs and 
the absence of horny tips on the branches of the first pleopods) which are 
like those of liis subgenus Paracambarus. Nevertheless, as Andrews has 
demonstrated the presence of a spine on the sternum of the last thoracic 
segment in two of Ortmann’s subgenera other than Paracambarus, i. e., 
in Procamharus (in the form of a rounded tubercle) and Cambarcllus, 
the writer would assign C. rutlweni to the subgenus Procambarus. 
Dr. Ruthven says that the species is a burrower, and that the burrows 
are common along the drainage ditches on the low land at Cuatotolapam. 
9. Macrobrachium acanth nr us (Wiegmann). — Several specimens were 
taken in seines from the Hueyapam River at Cuatotolapam. It was 
quite abundant along the shores. 
10. Macrobrachium olfcrsii (Wiegmann). — Two specimens were taken 
in the seines with the last species. 
11. Tricho dactylus constrictus, new species. — The following descrip- 
tion is from a female (41717) bearing young under her abdomen. 
Carapace punctate above; front margin slightly concave, smooth, 
slightly reflexed. 77-shaped depression well defined; posterior ends of 
lateral margins strongly narrowed, posterior seventh of carapace % 
as wide as greatest width ; three antero- lateral spines, first one some 
distance behind the orbit; gastric region strongly elevated. Front 
abruptly deflexed; orbital sinus in front of carapace rather deep. An 
obtuse spine at the ventral inner angle of the orbit; an elevated ridge 
on outer and ventral margins of orbit. Maxillipedes : eschium with inner 
and outer margins about equal in length; merus with inner margin 
as long as outer; exognath almost as long as endognath. Chelipeds: 
merus with a pointed spine on the inner and one on the outer margin 
below; also a spinous tubercle at the outer distal angle; carpus indis- 
tinctly punctate, a spine on the inner margin ; hand rather flattened, 
punctations faint and tending to cause low transverse ridges, margins 
subparallel; fingers flattened, a prominent ridge on upper surface of 
each, gaping very little at base; nine denticles on moveable finger and 
eight on fixed finger, these are larger toward the distal ends of fingers. 
Ambulatory legs little compressed except the fifth pair, all sparsely 
pilose. Abdomen and under surface of body not punctate. Length of 
abdomen, 16.3mm; width, 14.6. Length of carapace 17.5; width, 19. 
The above description was made from a specimen taken at Lake Cate- 
maco, July 27. Dr. Ruthven reports that it was collected with eight 
other females (No. 41718) along the lake shore under rocks which were 
not submerged or even washed by the waves. Four of the individuals 
