Further Notes on the Anatomy of the Heloderma

Abstract

SINCE I published in NATURE (vol. xliii. p. 514), “The Poison Apparatus of the Heloderma,” there has appeared from the pen of Mr. Boulenger another notable contribution to the anatomy of that genus of reptiles, entitled “Notes on the Osteology of Heloderma horridum and H. suspectum, with Remarks on the Systematic Position of the Helodermatidæ and on the Vertebræ of the Lacertilia,” (P.Z.S., January 20, 1891). That paper is especially useful, inasmuch as it critically compares the vertebral columns of the two species of Lizards under consideration—a comparison which, up to the time of the appearance of Mr. Boulenger's paper, had not been made. To briefly recapitulate his points, Boulenger finds differences in the form of the premaxillaries of the two species, and in the number of teeth supported by those bones. He finds palatine and pterygoid teeth constantly absent in H. suspectum but present in H. horridum—a very remarkable fact. A small azygous ossification was found in the cartilage of the mandibular symphysis of H. horridum, “apparently the homologue of the symphysial (mento-meckelian) bones of most tailless Batrachians.” This last discovery has important bearings in other directions. In the vertebral column there appear to be a total of 76 vertebræ in the case of H. horridum to but 63 or 65 in the spine of H. suspectum. And, in conclusion, this distinguished herpetologist remarks that “A short rib is present on the third cervical in H. horridum, which is absent in H. suspectum; the neural spines are more elevated in the middle and posterior portion of the dorsal region in H. horridum, specimens of the same sex, of course, being compared. The neural spines are much more developed in the male” (p. 116). Boulenger still thinks the place of the Helodermatidæ between the Anguidæ and the Varanidæ, which he assigned to them in 1884.