5 
Nannastacus are the eyes separated by a distinct interspace. The structure of 
the eyes is rather simple, and they contain only a very limited number of visual 
elements, corresponding to an equal number of more or less refracting corneal 
lenses of the integument. In the adult male, they are generally more fully devel¬ 
oped than in the females. 
The superior antennae are rather small, each consisting of a 3-articulate 
peduncle, and 2 diminutive flagella, the inner of which is sometimes quite obso¬ 
lete. The outer flagellum is tipped with one or 2 slender sensory filaments, and 
in the adult male, an additional bundle of such filaments is generally attached to 
the base of this flagellum. 
The inferior antennae are in the female, as a rule, very small and rudi¬ 
mentary, whereas in the adult male they are greatly developed, generally at¬ 
taining the length of the whole body. In structure, they resemble those in the 
male Phyllocarida and Ampliipoda, each consisting of an angularly bent peduncle, 
the outer part of which is densely clothed with sensory fiaments, and, together 
with the slender, multiarticulate flagellum, extends straight backwards. They are 
generally borne closely applied to the sides of the body, and thus easily escape 
observation ; but they admit of being moved from this position, and are probably 
subservient to copulation. This could be directly proved in the species of the genus 
Lam/props, where they are used as true prehensile organs, to obtain a hold of the 
female during copulation. 
The oral aperture is bounded in front by a generally small and simple, 
rounded anterior lip (which is more strongly developed only in the genus Cam- 
pylaspis ), and behind by a lamellar, bilobed posterior lip. 
The mandibles are strongly incrusted, and are in no case provided with 
palps. They are articulated to the inner side of the carapace just at the points 
where the diverging fissures encompassing the frontal lobe, terminate, and they are 
extended obliquely in front. The masticatory part is divided into 2 diverging 
rami, the anterior representing the cutting part, the posterior the molar expans¬ 
ion. The latter, in the greater number of forms, is rather thick, cylindric, and 
exhibits at the end a finely fluted triturating surface. The former has generally 
a dense series of curved spines immediately behind the cutting edge. 
The anterior maxillae exhibit the 2 usual incurved lobes, the masticatory 
and basal, the former being much the stronger, and armed at the obliquely 
truncated tip with short spines. The palp is peculiarly modified, and turned 
straight backwards, terminating in one or 2 band-like bristles, which project 
into the branchial cavity. It is wanting in 2 of the known genera, viz., Para- 
lamprops and Platyaspis. 
