LITHOTRYA N1COBARICA. 359 



segments on the usual structure. Third cirrus, longer, to 

 a remarkable degree, than the second cirrus, with its an- 

 terior ramus having the four basal segments paved, and 

 the seven terminal ones on the usual structure ; posterior 

 ramus with twelve segments, of which none are paved. 

 The pedicels of the second and third cirri thickly and 

 irregularly clothed with spines. The upper segments of 

 the pedicels of all the cirri are unusually long. 



Caudal dppendages, longer than the pedicels of the sixth 

 cirrus, by barely one third of their own length. Segments 

 much elongated, seven in number ; I may add for com- 

 parison that each ramus of the sixth cirrus contained, in 

 this specimen, sixteen or seventeen segments. 



General Remarks. — It is difficult to give obvious cha- 

 racters, (excepting the smallness of the rostrum compared 

 with the scales on the peduncle,) by which this species can 

 be externally discriminated from L.dorsalis, L. Nicobarica, 

 and L. Rhodiopus; yet almost all the valves differ slightly 

 in shape. In this species alone, (the peduncle of L. Rho- 

 diojpus is not known,) the lower, microscopically minute, 

 bead-like scales of the peduncle are crenated, though ob- 

 scurely, all round. In the animal's body, the diagnostic 

 characters are strongly marked ; — the long spines on the 

 terminal segment of the first cirrus, — none of the seg- 

 ments in the posterior rami of the second and third cirri 

 being thickened and paved with bristles, — the pectina- 

 tions being equal in number between the main teeth of 

 the mandibles, — are all characters exclusively confined to 

 this species. 



3. LlTHOTRYA NICOBARICA. PI. VIII, fig. 2. 



L. nicobaiiica. Reinhardt, Naturhist; Selskabet, 



Copenhagen. No. I. 1850. 

 Tab. I, fig. 1—3* 



* I am not at all sure that the proper title of the periodical in which this 

 species has been described, is here given. I am greatly indebted to Prof. 



