1888.] AUSTRALIAN ( 



suddenly bends downward with a very sharp and abrupt curve, 

 giving this part of the carapace a somewhat gibbous aspect; it 

 terminates at the tip of a broadly rounded projection, located a 

 little above the longitudinal axis of the carapace. The free edges 

 of the valves are slightly concaved anteriorly at the side of the 

 mandibles, below the head however bulging out considerably and 

 forming a rather promineut curve; the inferior edges are nearly 

 straight in the middle, but posteriorly they successively curve 

 upwards, joining the very oblique posterior edges which ter- 

 minate at the tip of the above-mentioned obtuse projection, with- 

 out forming any distinct sinus. — The head, as seen laterally, 

 is comparatively small, much narrower than the carapace, and 

 of an oblique triangular form, its dorsal edge exhibiting a per- 

 fectly uniform curve, which forms the continuation of the dorsal 

 edge of the carapace. Anteriorly it terminates quite abruptly, 

 the front being at this point produced to a right-angled projec- 

 tion, whence the ventral edge extends posteriorly, with a straight 

 course, to within a short distance from the insertion of the an- 

 tennulse; at this point the head juts out as a short acute, some- 

 what recurved projection or beak, defined from the ventral edge 

 by an angular notch. Viewed from above or below (fig. 2), the 

 head exhibits a rather different form, being very broad and cly- 

 peiform. This is caused by the greatly developed fornices, which 

 issue from the sides of the head and cover over the bases of 

 the antennae. Also in a lateral aspect these fornices admit of 

 being traced with comparative facility as a sharply marked, 

 somewhat flexuous line, running from the front obliquely back- 

 wards and joining the carapace at the point where the free edges 

 of the valves take their origin; moreover the line is continued 

 back from this point to the dorsal edge, marking off from the 

 carpace a triangular dorsal area. Just in front of this area 

 there is a very slight impression in the dorsal edge, indicating 

 the limit between the head and the trunk, and this impression 



is bounded anteriorly by a small projection 



ing organ. Also the carapace, when viewed dorsally 



