REPORT ON THE CRUSTACEA MACRURA. 595 



Spirontocaris, 1 n. gen. 



Hippolyte, Leach, Malacos. Pod. Brit. (Division **). 



„ Milne-Edwards, Hist. Nat. Crust., torn, ii., pp. 375, 37S (Divisions 2 and 3). 



Eell, Brit. Stalk-eyed Crust., p. 283 (Part). 

 ,, Dana, U.S. Explor. Exped., Crust., p. 505 (Division 2). 



„ Stimpson, Proe. Acad. Nat. Sci. Philad., p. 102, I860. 



Carapace carinated and armed with teeth. Rostrum deep, laterally compressed 

 and armed on the upper and lower margins with numerous strong teeth. Frontal margin 

 having two supraorbital, one antennal and one fronto-lateral teeth. First pair of 

 pereiopoda subecmal, having the carpos not excavate at the anterior extremity. Second 

 pair having the carpos seven-jointed. Branchiae twelve. 



The carapace is anteriorly carinated and produced to a laterally compressed rostrum, 

 that is furnished with teeth on the upper and lower margins, and elevated to a crest over 

 the gastric and frontal regions. The frontal region is armed with two supraorbital teeth 

 and an antennal tooth, and one is situated at the infra-anterior angle of the carapace. 

 The pleon is dorsally smooth, having the third somite arcuate and posteriorly produced 

 in the median line over the fourth somite. 



The ophthalmopoda are uniarticulate, pyriform, short ; the ophthalmus being 

 furnished with an ocellus. 



The first pair of antennae is but little longer than the rostrum, having the first joint of 

 the peduncle slightly excavated, broadly expanded, and armed on the outer margin with 

 a stylocerite that is subequal in length with the first joint of the peduncle. The second 

 and third joints are cylindrical, and support two short unequally stout flagella. 



The second pair is subecpial in length with the animal, and has a scaphocerite that 

 is armed with a tooth on the outer distal extremity. 



The mandibles have a broad molar process that is curved at right angles to the 

 apophysis ; the psalistoma is rudimentary and not connected with the molar process ; 

 the synaphipod is small, feeble and two-jointed. 



The first pair of gnathopoda is small, feeble, and of great tenuity ; the carpos and 

 propodos are compressed, dilated, and reflexed against the inner margin of the mei'os ; 

 the basis carries a long ecphysis and the coxa supports a mastigobranchial plate, to which 

 is attached a small podobranchial plume. 



The second pair of gnathopoda is subpediform and five -jointed, the terminal joint 

 is longer than the preceding, and distally compressed, the basis furnished with a short 

 ecphysis, and the coxa carries the rudiment of a mastigobranchia but no branchial plume. 



The first pair of pereiopoda short, robust and chelate, having a carpos that is 

 anteriorly as broad as the proximal extremity of the propodos. The second pair is 

 more slender than the first, minutely chelate and unequal in length, having the carpos 



1 From tnai^m, a sower. 



