1893.] Structure of Carapace in Rhinocaris. 795 
of a low pustule with a single central depression or pit. From 
the base of this node radiates a series of linear, sparsely 
branching sinuses which extend laterally and posteriorly 
toward the marginal regions, the longest traversing nearly 
one-third the length of the valves. There isa very faint ridge 
or carina which lies just outside the middle of each valve and 
extends subparallel to the outer margin, for nearly the length 
of the valve, though reaching neither its anterior nor posterior 
margin. 
In addition to these characters, the valves, over the margi- 
nal regions, bear the fine anastomosing elevated lines which 
characterize all the phyllocarid crustacea. 
The rostrum is an elongate plate having, when flattened hori- 
zontally, somewhat the form of a willow leaf. Its broader end 
is inserted into the anterior gap between the valves and its pos- 
terior extremity is acute. As the plate begins to project beyond 
the anterior edge of the valves of the carapace, it narrows, its 
lateral expansions become deflected, the median portion taper- 
ing rapidly and becoming slightly incurved toward the tip. 
The plane of the anterior half of the plate stands at 
nearly right angles to that of the posterior half, as shown in the 
accompanying figures. That this organ is in symphysis with 
Fic. 2. Dorsal view and outline profile of the rostrum of Khinocaris columbina, 
the valves is evident from the fact that it is rarely found in its 
normal position. The surface is peculiarly ornamented by a 
series of elevated lines forming a sort of midrib ; over the lat- 
eral posterior expansions the lines become much finer, diverge _ 
