228 Zoological Society. 



Nymnion Phasma, White. 



Head with a longish neck, the greater part of which is as thin as 

 or thinner than the articulations between the legs, thickened in front. 



Beak thick, blunt, and somewhat knobbed at the end. 



Eyes two, situated on a sharp-pointed tubercle, placed between 

 the first pair of legs, somewhat in front of insertion. 



Chelicera somewhat longer than the beak, thick, two -jointed; 

 second joint rounded, furnished with two claws which meet through- 

 out. 



Palpi elongated, filiform, 10-jointed; three basal joints small; 

 fourth joint very long ; fifth joint shorter than the fourth, with a 

 slight hook at the end ; sixth joint about the same length as the fifth, 

 but without hook at the end ; four last joints short, somewhat curved. 



Legs eight, somewhat hirsute, the third leg perhaps shorter than 

 the others. 



Tarsi with one claw, the under-side furnished with many small 

 spines. 



Hab. South Seas. Capt. Sir Edw. Belcher, R.N. 



This may possibly be the other sex of the preceding. Neither of 

 them have any trace of oviferous legs. 



Additional Observations on Chitones. By J. E. Gray, Esq., 



F.R.S. ETC. 



Since the publication of my former paper I have continued my 

 researches on these animals, and now propose to add four groups to 

 those which I then described : three of these genera were proposed 

 as sections of the genus Chiton in my former paper, but I have since 

 found that they each present peculiar modifications in the structure 

 of the plate of insertion of the valves ; and the other is a genus which 

 I had overlooked, though founded on two of the English species of 

 the family. On re-examination I think that the genus Chiton should 

 be confined to the species which have a single notch on the plate 

 of insertion of the central valves, and the edge of the plate of inser- 

 tion pectinately lobed, which is the case with the species marked as 

 belonging to the section * and ** (Annals, vol. xx. p. 131.), except 

 Chiton Barnesii and Ch. evanidus. 



1. Radsia. 



Posterior valve entire ; margin covered with regularly -disposed im- 

 bricated smooth scales ; margin of insertion of the central valves 

 pectinately divided, and each furnished with two notches. 



Radsia Barnesii. Chiton Barnesii, Gray. 



2. Callochiton. 

 The valves keeled, the hinder valve entire ; the plates of insertion 

 rather short, thick, of the terminal valves divided into many, and of 

 the central valves into four bifid lobes. Margin with imbricate 

 scales. 



* Margin with lanceolate, elongate, erect, closely -pressed scales. 

 Callochiton lrevis. Chiton lcevis, Mont., Lowe, Z. Jour. v. t. 5, f. 1 . 



