Miscellaneous. 145 



these two divisons, which he proposed to call suborders of Dr. Dana's 

 order Merostomata. He also pointed out that the Xipkosura were 

 divisable into three genera : — 1st, Belinurus, Baily, having 5 freely- 

 articulated thoracic segments, and 3 anchylosed abdominal ones and 

 a telson ; 2nd, Prestwichia, a new genus, having the thoracic and 

 abdominal segments anchylosed together ; and 3rd, Limulus, Miiller, 

 having a head composed of 7 cephalic and 1 thoracic segments, 

 followed by 5 coalesced thoracic somites bearing branchiae, and 1 or 

 more coalesced apodal abdominal somites, to which is articulated 

 the telson. Although so great a dissimilarity exists between Ptery- 

 gotus and Limulus, yet in the genera Hemiaspis, Exapinurus, and 

 Pseudoniscus we have forms which, in the number of body-rings, 

 are intermediate. 



The order Merostomata offers a parallel group to the Decapoda, 

 the Eurypterida representing the Macrura, and the Xipkosura the 

 Brachyura. The author did not, however, intend by this comparison 

 to indicate that Limulus was higher in the Crustacean scale than 

 Pterygotus, but rather that the former was one of those low but 

 persistent types (like the Brachiopoda) which have remained un- 

 changed through long geological ages, whilst forms capable of 

 further development, like Pterygotus, have been modified and swept 

 away. — Proc. Geol. Soc. Nov. 21, 1866. 



On the Structure of the Skin in Stellio caucasicus. 

 By Professor F. de Filippt. 



In his travels in Georgia and Persia, M. de Filippi observed the 

 Stellio caucasicus in great abundance and at the most various eleva- 

 tions. Contrary to Dumeril and Wilson's account of the habits of 

 Stellio vuJgariSy he ascertained, by the dissection of a great number 

 of individuals, that this animal feeds chiefly upon vegetable materials, 

 and that insects form but a small portion of its nourishment. This 

 fact is not without interest, as the known herbivorous Saurians 

 {Iguana^ Amblyrhynchus, Cycluray Sauromalus) are peculiar to 

 America. 



But the most remarkable peculiarity of this species consists in a 

 change of colour under the influence of light, perfectly similar to 

 that of the Chameleons. An analogous phenomenon has certainly 

 been mentioned as occurring in other Saurians, especially in certain 

 species of Jgama, Anolis, and Polychrus ; but nothing of the kind 

 had previously been suspected in any Stellio. The scale of variation 

 of colour, indeed, is greater in the Chameleons than in Stellio cauca- 

 sicus ; but, on the other hand, the latter seems to present a greater 

 distance between its maximum paleness and its most complete dark- 

 ening ; in other words, the phenomenon is more varied in the Cha- 

 meleon, and more striking in the Stellio, Moreover these changes 

 of colour occur only in the adults, the young being exempt from 

 them, contrary to what is observed in the Chameleons. The change 

 is particularly distinct on the lower part of the body, and diminishes 

 towards the back. The Chameleon becomes dark when it is exposed 



