50 G. S. WEST. 



what rouglily investigated its general structure in Crotalus 

 horridus, Lachesis (Trigonoceplialus) puniceus, and 

 L, atrox, and described the nature of the nerve terminations 

 in the organ. It was pointed out in Bronn's ' Klass. u. 

 Ordnung. Thier-Eeichs/ Rept. Ill, Schlangen, 1890, p. 1411, 

 that the skin of the pit is not itself fixed to the hollow of the 

 maxillary bone ; and although this is the first mention of 

 what is, perhaps, one of the most important featui'es in the 

 structure of the organ, it is a somewhat erroneous statement. 

 The membrane stretched across the hollow in the maxilla 

 is not the '' skin of the pit," but a thin partition (which I 

 shall fully describe further on) dividing the pit into two 

 chambers. 



The peculiar osteological characters of this region of the 

 skull are mentioned by Peters^ and also described by Taylor.^ 



The present investigation, which can obviously be little 

 more than an account of the anatomy and histology of the 

 organ, was undertaken at the suggestion of Dr. Gadow, to 

 whom I offer my best thanks for sundry information and for 

 specimens of Lachesis lanceolatus, Moreau,and L. suma- 

 tranus, Boul., from the Museum of Comparative Anatomy 

 at Cambridge. 



The greater part of my material was very kindly supplied 

 to me by Mr. Gr. A. Boulenger from the duplicate specimens 

 in the British Museum. I have to tender him my sincerest 

 thanks for specimens of Lachesis gramineus, Russell, L. 

 mutus, Seba, L. atrox, Boul., Crotalus triseriatus, Boul. 

 (young and adult), and C. terrif icus, Seba; also for embryos 

 of Crotalus scutulatus, Boul., Ancistrodon Blomhoffii, 

 Boul., and Lachesis nummifer, Boul. In addition to these 

 I had in my possession adult specimens of Ancistrodon 

 Blomhoffii from Japan, and a species of Crotalus from 

 North America. 



^ TV. Peters, " Ueber die craniologisclien Verseliiedenbeiten der Grubenot- 

 tern (Trigonocepbali)," 'Berliner Moiialsb./ 1862, p. 670. 



' W.E.Taylor, "Prelim. Notes on the Osteol. of the N A.tner. Crotalidse," 

 ' Amer. Naturalist,' March, 1895, p. 282. 



