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Show 1890.] HELODERMA S U S P E C T U M. 209 insertions as seen in the Lizards generally, the following muscles were examined, viz :- 122. Rectus anterior. 123. Rectus posterior. 124. Rectus superior. 125. Rectus inferior. 126. Obliquas superior. 127. Obliquus inferior. 128. Musculus choanoides. 129. Pyramidalis. 130. Levator palpebraj superloris. 131. Depressor pulpebrce inferioris (feebly developed). 132. Orbicularis palpebrarum (feebly developed). The pupil is round, and the sclerotal plates are thin, these latter having each a form somewhat similar to what we find in Birds. Careful examination failed to demonstrate the presence of the pecten within the eyeball, though future specimens may go to show its presence. It is known to be absent in Hatteria and Chelonia1. Around the entrance of the optic nerve the sclerotic coat seems to occasionally slightly ossify. I have also found this to be the case in a variety of genera of Birds. W e find the cornea to be not very markedly convex, while the lens is comparatively of good size, it being quite flat externally, and convex upon its internal aspect. X. NOTES ON THE ANATOMY OF THE EAR. Heloderma has the tympanum of the ear large and fully developed, making the usual attachments to the parts and bones in the vicinity, thus creating a capacious meatus. Upon dividing this, the external ear-drum, all around at its periphery, and reflecting it, we bring into view the cartilagino-osseous chain of elements that connect the tympanum with the inner ear. Both the passage of the Eustachian tube and the cavity of the middle ear are capacious. Lying along the dorsal roof of this chamber, and close to it, we observe the well-developed columella auris; it passes forwards and inwards and very slightly upwards ; tbe osseous rod-like portion being included in a fold of the common lining epithelium, as is likewise the infra-stapedial process in its own fold. The middle ear is partially divided into two cavities by the inner edge of the quadrate bone, and we see that it is within the inner part of this cavity that the ossified medio-stapedial portion of the columella auris lies, while the outer cartilaginous extremity of the rod 1 Since writing the above I have carefully examined an eye in very fair condition from an alcoholic specimen of Heloderma suspectum, and in it I discovered an extremely delicate fold of tissue extending from the capsule of the lens to a point near the entrance of tbe optic nerve. It was non-pigmented. This structure quite possibly represents the pecten or "falciform process," but it is here by no means so well marked as I have found it in many species of Birds. Of course the demonstration of the presence of a tapetum in old alcoholic specimens of Heloderma is difficult, and I was not successful in any instance. |
