320 CRUSTACEA. 



form is very much as in Gelasimus. There is no hiatus in the outer 

 margin of the orbit in the species seen by us. The sulci of the outer 

 maxillipeds converge backward, and have the form of a letter V, with 

 the sides convex outward. The aspect is somewhat like that of Gono- 

 plax ; but the third joint of the outer maxillipeds bears the following 

 at its outer instead of inner angle, and the fourth joint has the outer 

 surface more convex. The front in our species is very narrow, but 

 not narrower between the eyes than below. The under surface of the 

 third joint of the six anterior legs is densely hairy or woolly, which is 

 not true of any Gelasimi, as far as observed by the writer. The male 

 abdomen widens a little towards its base, and its first or second joint 

 is hardly narrower than the third, and as wide as the sternum corre- 

 sponding. The lateral margin in the species is somewhat convex 

 anteriorly, the greatest breadth being posterior to the anterior angles. 

 The genus is evidently intermediate between Gelasimus and Doto. 

 The name is derived from i*o ( , marsh, and o^?, house. 



Helcecius cordiformis {LatreUle), Dana. 



Plate 19, fig. 6 a, natural size ; b, hand, natural size. 



New South Wales. 



Length of carapax of a male, seven and a half lines; breadth, 

 eleven and three-fourths lines; ratio, 1:1*57; length of larger hand, 

 with moveable finger extended, fourteen lines ; of same, to apex of 

 lower finger, eleven and a half lines ; length of carpus, five and one- 

 third lines, and breadth, two and a half lines ; length of hand, ante- 

 rior to fingers, measured to lower basal angle, eight and one-third 

 lines, and breadth, four lines. The last segment of the male abdo- 

 men is not as short transverse as in the inornatus, and though narrower 

 than the preceding, is not abruptly so ; it appears to have a triangular 

 form, owing to the dense hairs at apex; the other abdominal segments 

 also are shorter transverse. The hand enlarges from the base out- 

 ward, and the part below the fingers is more oblong than in that 

 species, and somewhat triangular in form. The buccal mass is more 

 projecting. We have suspected that the inomatus may be only a 

 younger condition of the cordiformis; but the size is not very unlike, 



