1890.] HELODERMA SUSPECTUM, 211 



There is before me at the present moment a mounted skeleton of a 

 Heloderma suspeclmn belonging to the U. S. National Museum, 

 wherein the hinder third of the skeleton of the tail has been replaced 

 by feebly developed cartilaginous nodules, and it is very evident that 

 that specimen, in life, sometime or other lost that part of its economy. 



The Lymphatic system of Heloderma has not been examined by me ; 

 that is beyond what I have given above in reference to the spleen. 



XII. Some Observations upon the Nervous System. 



Although it possesses a peculiar fades of its own, the brain of 

 Heloderma suspectum is quite typically Lacertilian in the majority of 

 its parts. Either olfactory lobe is ralher short, comparatively, and 

 is of nearly uniform calibre throughout. The outer envelope of the 

 brain enslienths these lobes together, up to their anterior tips. 

 Measuring from the posterior surface of the cerebellum to the tip of 

 an olfartory lobe, the greatest length of the brain of this reptile is 

 2''.') centimetres, while is greatest width, taken through the cerebral 

 mass transversely, is one centimetre. Each cerebral hemisphere is 

 reniform in outline, full, and beautifully rounded. The posterior 

 limbs of the somewhat slender optic chiasma are closely applied to 

 the rather large pituitary Ijody, which latter presents the usual 

 infundilmlum, and withal has a form much as we tind it in Lacerta 

 viridis. Upon opening one of the cerebral hemis|)heres we observe 

 that the corpus striatum is large and rounded and occupies consider- 

 able space in the central cavity. A choroid plexus is easily made out. 

 Turning to [he pineal body weHind it small and rather inconspicuous, 

 and when the brain is in its case in situ within the skull this structure 

 comes closely in contact on the ventral surface, in the middle line, 

 with a large longitudinal venous sinus that is seen in this cavity in 

 Heloderma. I have made no especial histological examination of 

 the pineal body in our present subject, and consequently cannot with 

 authority say at what stage the " parietal eye " maybe: lam of 

 opinion, ho\vever, that it is undoubtedly in a very rudimentary 

 condition. It is a fact that a very considerable venous sinus stands 

 between it and the cranial roof, and that not a vestige of a parietal 

 foramen is to be found piercing the latter. This latter feature is 

 well seen in a skull of Iguana tuberculata before me that belongs 

 to the collections of the Smithsonian Institution (No. 12600). After 

 reading Baldwin Spencer's announcement of his important discovery, 

 it is quite natural that this point should specially interest me upon 

 dissecting the brain of Heloderma ^ 



Young Heloderms show no better development of this eye than 

 do the adult specimens, in so far as I have examined them. 



Passing to the olfactory lobes, we find them to be rather small in 

 comparison with the size attained by the heniispheres in the Lizard 

 before us, the two lobes together barely having a width equalling the 

 width of one of the hemispheres. 



' Spencer, W. Baldwin, " The Parietal Eyo of Huilena." ' Nature,' May l.'5lli. 

 1880, p. 33. 



