260 CLASS XV. 



are accommodated to the shape and size of the second projection of the new 

 piece, whilst the second swelling which secreted the second projection of 

 the piece takes the dimensions suited to the third projection of the future 

 new piece. It is further supposed that these two swellings are caused to 

 move from before backward by the development of a new swelling of the 

 skin suited to the dimensions of the first projection of the new piece which 

 is to be secreted by it. It will be understood that all that is visible of the 

 rattle externally is the surface of the basal projections or rings of each 

 succeeding joint. The first joint alone has vital connexion with the skin 

 of the animal ; it is caused to vibrate by the muscles of the skin, and its 

 vibration commanicates a quivering motion, accompanied by sound, to the 

 dry homy pieces behind it. See J. CzEEMACK Uher den schallerzeugenden 

 Apparatvon Crotaliis. Zeitschr. f. ivissenscJi. Zool. viii. 1856, pp. 294 — 301, 

 Taf. XII. 



The species of this genus are all found in America. They are highly 

 venomous, but dull. The species from South America (fi-om Surinam, 

 Brasil).has not only the part of the head in front of the eyes covered 

 with scutes, but also four small scutes above the eyes. This appears to be 

 the species which may be regarded as Crotalus Durissus L. On the back 

 are seen rhomboidal spots lighter in the middle. Vosmaer Beschrijv. van 

 eene Surinaamsche ratelslang, 1768, 4to; Maxim. Ahh. zur Naturgesch. 

 Brasil. Lief. xi. ; Cuv. R.Ani., ed. ill., Rept. PI. 32, A large species from 

 North America has scales between the eyes and brown transverse bands, 

 Crotalus horridus L., Guerin Iconogr., Rept. Pi. 23, fig. 2, Crotalus du- 

 rissiis HoLBR., N. American Herpetology, 11. PI. 17. Daudin, Schlegel, 

 and DuMERiL make an opposite use of these Linnean names. — A smaller 

 species from North America, Crotalus milianus L., has a more oval head 

 covered with scutes (one scutum vertebrate and two scuta occipitalia). 

 HoLBR. 1. 1. Vol. II. PI. 15. 



Trigonocephalus Oppel, Cophias Mereem. Tail round, with 

 apex simple, conical; several subcaudal scutes in pairs, with un- 

 paired interposed. Remaining characters those of the preceding 

 genus. 



a) With head scaly. 



Cophias BoiE. {Lachesis Daud., Craspedocephalus Kuhl, Bothrops Wag- 

 LER, &c.) 



Sp. Trigonocephalus crotalinus nob., Crotalus mufus L., Schleg., Lachesis 

 rhoinieata Maxim. Abb. z. Natitrg. Bras. Lief. V. Suruhuku {Curucucu 

 Marcgr.) ; the tail has at the base first two or three undivided scutes ; to 

 these succeed the paired scutes ; the extremity of the tail both above and 

 below is covered with scales, and terminates in a homy point. This serpent 

 is found in Guiana and Brasil, and is very dangerous ; it attains a length 

 of 10'. 



Trigonocephalus atrox Schleg., Coluber atrox L., Mus. Ad. Frid. Tab. 

 22, fig. 21; Brasil, Surinam; — Trigonocephalus viridis Cuv., Bothrophis 



