REPORT ON THE CRUSTACEA MACRURA. 139 



a line with the posterior margins of the orbits is a single sharp tooth ; at an equal 

 distance behind is a second, behind which, at a similar space, are two side by side, pos- 

 terior to which is another single tooth. These are all anterior to the cervical fissure, on 

 the posterior margin of which two teeth stand close together, while scarcely half way 

 between these and the posterior margin are two others placed side by side, and two others 

 wider apart stand upon a protuberance on the ridge of the posterior margin. The line of 

 demarcation that separates the branchial chamber from the internal viscera is clearly de- 

 fined, and armed with a tolerably strong tooth near the posterior extremity, and indica- 

 tions of others exist along the line. 



The pleon gradually narrows towards the posterior extremity of the animal, and is 

 armed in the median line of the five anterior somites with a series of strong anteriorly- 

 directed teeth which gradually increase in size posteriorly, so that the fifth is the largest. 

 On the sixth somite there is no tooth, but there is a double ridge that unites in front of 

 the posterior margin. 



The telson is long, narrow, and pointed. 



The ophthalmopoda (PL XIV. fig. 2c, a) are rather broad and distinct on the dorsal 

 surface, the anterior margin of which is armed with a small outwardly- directed tooth. 

 Judging by the translucent appearance of the external tissue, one lens appears to be 

 situated at the posterior dorsal extremity of the orbit, and another on the anterior 

 point of the ophthalmopod, which is depressed and covered by the anterior angle 

 of the carapace, and projects outwards between it and the second or outer pair of 

 antennae. 



The first pair of antennas (fig. 2c, b) has the first joint produced internally and anteriorly 

 to a point that reaches as far as, or beyond, the extremity of the third joint of the 

 peduncle, and thins out to a ridge that is directed obliquely upwards, and is not armed 

 with teeth but fringed with hairs only. A large round lobe, containing the auditory 

 apparatus, exists within the outer margin, the oj>ening to which consists of a narrow 

 transverse slit armed at the outer margin with two sharp, strong teeth, one anterior 

 and the other posterior to the opening. The second and third joints are cylindrical 

 and successively smaller, and support two flagella of which the inner is as long as 

 the carapace, the other is slender and short, being but little longer than the peduncle of 

 the antenna. 



The second pair of antenna? (fig. 2c, c) articulates with the metope entirely ; the 

 coxa being free carries a long and prominent phymacerite, the extremity of which is 

 compressed against the surface in a depression on the under side of the first pair of 

 antennas. The second joint carries on the outer anterior extremity a long narrow ovate 

 centrally-pointed scaphocerite ; the third and fourth joints are cylindrical and equal in 

 length, and the terminal fiagellum is as long as and resembles that of the internal of the 

 first pair. 



