MUSEUM OF COMPARATIVE ZOOLOGY. 151 
from the cavity of the orbit by a broad process of the bail segment. Merus 
of outer maxillipeds notched at the antero-internal angle. Legs of moderate 
length ; carpus of chelipeds elongated, not carinated; chela elongated and 
slender, fingers canaliculate within, but not spoon-shaped at their tips, their 
prehensile edges meeting throughout most of their length, not distinctly 
toothed ; ambulatory legs spinose. Abdomen (male) seven-jointed, terminal 
joint short and broad. 
This genus is proposed for the reception of an interesting Maioid dredged 
in 182 fathoms on the west coast of the Isthmus of Panama. It combines 
in one form characters of the genera Maia, Cyclomaia, Paramithrax (subg. 
Leptomithrax), and Schizophrys. In its general aspect it bears a close resem- 
blance to Maia, and the likeness is enhanced by the small eyes and slender 
eyestalks, the elongated wrist and hand, and the short epistome. It differs 
from Maia in having a much broader carapace, a less deeply cloven rostrum, 
spinose legs, supra-ocular spines, and trenchantly in the exclusion of the an- 
tennal flagellum from the orbit by a process of the basal segment of the antenna. 
In the latter regard it agrees with the genus Cyclomaia, the basal segment of the 
antenna being very broad, three-spined on its distal border, and giving off a 
process which separates the flagellum from the orbit by a wide interval; it also 
agrees with Cyclomaia in having a short epistome, a short and broad terminal 
abdominal segment, and supra-ocular spines. It differs from Oyclomaia by 
having a subtriangular carapace, longer rostral spines, and a less abruptly 
declivous front. It is like Paramithrax and Schizophrys in the exclusion of 
the basal antennal segment from the orbit, but this segment is much broader 
than in these genera, and three-spined; moreover, Matopsis differs from Para- 
mithrax and Schizophrys in having a more broadly triangular carapace, supra- 
ocular spines, slenderer wrist and hand, less deeply cleft rostrum, and spinose 
ambulatory legs. Like Schizophrys, it has an accessory spine on each rostra 
horn. In the shape of the carapace Maiopsis is intermediate between Maia 
and Cyclomaia. In the form of the fingers it stands between Maia and Para- 
mithrax on the one side, and Schizophrys and Cyclomaia on the other, as the 
fingers, though canaliculate within, are but slightly excavated at the tips. 
The synthetic character of the species upon which this genus is based suggests 
the propriety of ultimately extending the scope of the old genus Paramithrax 
so that it may embrace this form, together with Cyclomaia and Schizophrys. 
Maiopsis panamensis, sp. nov. 
Dorsal surface of carapace thickly set with spines of various sizes and scat- 
tered hooked sete. The largest spines are distributed as follows : five on the 
gastric region, one on the genital, one on the cardiac, four on the intestinal, 
and about seven on each branchial region. Margin of carapace armed with 
twelve prominent spines, three of which are on the hepatic region. The ster- 
num is ornamented with small tubercles along each side of the abdomen. The 
