REPORT ON THE CRUSTACEA MACRURA. 845 



This species is remarkable for the exceptional development of the tooth-like structure 

 on the posterior margin of the third somite of the pleon, which is developed in a carina- 

 like form and overhangs the two succeeding somites, while that on the fourth is shorter 

 and almost covered by it, giving the appearance of two projections from one somite. It 

 is not only the carina that projects but the dorsal surface of the somite is suddenly 

 produced on each side, halfway between the median line and the angle formed by the 

 coxal scale, at a right angle to the lateral margin, above which lies the laterally narrow 

 carina that increases in height as it projects posteriorly, whereas on each of the somites 

 anteriorly and posteriorly the carina is reduced in character, dying out on the first 

 and last somites, the terminal tooth of the somites gradually getting reduced in size 

 posteriorly. 



The ophthalmopoda are moderately long, slightly compressed transversely, and 

 furnished on the inner side with a small tubercle near the ophthalmus, which is hemi- 

 spherical ; it is lodged in a small notch -like orbit that is clearly defined by a rounded 

 outer canthus. 



The first pair of antennae has the peduncle very robust and short ; the first joint 

 extends beyond the extremity of the rostrum, and is deeply excavate for the reception 

 of the ophthalmopod ; on the outer side there is a short stout stylocerite, the external 

 surface of which is vertical or nearly so, and terminates in a small sharp tooth that 

 reaches to about half the length of the joint. The cilia that form the blepharis so 

 common in most species is altogether absent, and this is apparently not the result of 

 accident, but indicates the permanent condition. 



The second and third joints are very short, cylindrical, and together are about half 

 the length of the first, and are very thick, the second more so than the third. The 

 flagella are very unequal, the upper and outer being much more stout than the inner and 

 lower ; the lower surface of the upper is flattened and occupied by a series of 

 membranous cilia. The lower flagellum is slender almost to the base, which is slightly 

 enlarged and conformable with the under surface of the upper ; both are obscurely 

 multiarticulate and free from hairs ; the length cannot be determined in this specimen, as 

 the organs are broken off short. 



The second pair of antennae has the peduncle very stout and carries an apparently 

 large scaphocerite, the length of which cannot be determined, but it appears to be more 

 rigid than the other organ, for which purpose it is strengthened by two long, narrow, rod- 

 like ridges, one on the outer margin within and parallel with it ; beyond the articulation 

 of the scaphocerite there are two well-developed and robust joints, of which the distal is 

 the longer and stouter. The flagellum is wanting. 



The mandibles and the oral appendages correspond closely with those of Notostomm, 

 scarcely exhibiting even a specific variation. 



The first pair of gnathopoda is seven-jointed and subpediform, and resembles that of 



