86 THE VOYAGE OF H.M.S. CHALLENGER. 



Geographical Distribution. — This restricted genus as far as known belongs to the 

 southern hemisphere. Palinostus lalandii ranges from the Island of Tristan da Cunha 

 to the Cape of Good Hope ; Palinostus frontalis is found on the coast of Chili, and 

 Palinostus hiigelii was taken in the Indian Ocean. 



Palinostus lalandii (Lamarck) (PL XL fig. 1 ; PI. XII. fig. 1 ). 



PaUnurus lalandii, Lamarck, MS., in Museum, Jardin des Plantes. 

 „ „ Milne-Edwards, Hist, des Crust., t. ii. p. 293. 



on PI. XL, fig. 1 ; PI. XII. fig. 1. 



Rostrum depressed and rapidly narrowing anteriorly to the apex, which has a tendency 

 to curve upwards; just within the apex are planted two vertical processes (fig. 10, p. 85) 

 that securely grasp the rostrum on each side. These calcified processes originate in the 

 anterior wall of the ophthalmic somite, which proceeds in a direct line beyond the vertical 

 processes, and terminate in an obtuse point on each side of the central line, corresponding 

 in length to the rostrum. 



In PaUnurus and Panulirus, the first antennal somite is largely developed and 

 forces the second pair of antennae widely apart ; in Palinostus lalandii it is reduced in size 

 and forced down below the second pair of antennas, which meet and articulate above 

 it. The first or coxal joint, in all species of this family, is closely impacted and 

 anchylosed with the anterior wall or metope of the cephalon, and meets its fellow in the 

 median line beneath the rostrum ; it sends forth a process that articulates with a similar 

 one projecting from the lower and outer angle of the second joint; the upper and 

 inner angle of the same joint articulates with a process which projects anteriorly from 

 the first antennal somite, below the- rostral points. This articulation is wanting in 

 both PaUnurus and Panulirus, and instead of it, the process of the antenna pro- 

 jects above and carries a membranous fold over the antero-lateral walls of the largely 

 developed first antennal somite, under which lies the stridulating organ. This organ 

 is absent in Palinostus. 



The first pair of gnathopoda has only six joints, the meros and ischium being 

 probably fused together into one which is short, thick, and scarcely longer than broad. 

 The carpos is short, triangular, and articulates laterally and bends suddenly ; the propodos 

 is broad and the dactylos short and wide ; the basal joint of the basecphysis is nearly as 

 long as the mero-ischial joint, and terminates in a long slender flagellum. 



The second pair of gnathopoda consists of seven joints, the meros and ischium 

 being free and articulated near the centre ; the carpos articulates at the extremity ; the 

 propodos is narrow, increasing slightly in length towards the distal extremity, which is 

 excavated to receive the. long, narrow, and obtuse dactylos. The whole appendage is 

 fringed with long hairs on the inner and distal surfaces. 



