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Show 1891.] ON HELODERMA HORRIDUM AND H. SUSPECTUM. 109 The fish is 19*5 cm. in length (with caudal) and weighs 74 grms. It is interesting to note that, in spite of its totally wanting one pair of organs of locomotion, the specimen had, when caught, every appearance of being in as good condition and as well nourished as the normal fish of about equal size obtained from the same shoal, and most likely therefore of about the same age. In connection with this case of abnormal absence of pelvic fins may be mentioned the fact that their normal absence among Teleostei is a much more frequent specific character than the absence of pectorals. Day 1 mentions that pelvic fins were entirely absent in eleven out of thirteen specimens of Gasterosteus pungitius obtained by him in Ireland, and when present were very small. This abnormality was accompanied by modifications or absence of the pubic plate and ventral spine. In all the examples of G. spinachia and G. aculeatus pelvic fins were present. I am indebted to Prof. G. B. Howes for a Goldfish, 7 cm. in length, in which the left pelvic fin is absent, the other being well developed. The abnormal Bream has been placed in the Museum of the Royal College of Surgeons. DESCRIPTION OF PLATE X. Fig. 1. Specimen without pelvic fins. Fig. 2. Outline of normal fish. Fig. 3. Ventral view of pelvic girdle and fins of 2. 5. Notes on the Osteology of Heloderma horridum and H. with Remarks on the Systematic Position of the Helodermatidce and on the Vertebrae of the Lacertilia. By G. A. BOULENGER. [Received January 6, 1891.] The skeleton of a fully adult specimen of Heloderma horridum, obtained by Dr. A. Buller in Mexico, has recently been prepared for exhibition in the galleries of the Natural History Museum, and at the same time Professor Stewart prepared a skeleton of an adult H. suspectum for the Museum of the Royal College of Surgeons. It appeared to me that it would be interesting on this occasion to make a comparison of the skeletons of the two species and to record whatever differences they might present; for although a good deal has been published on the osteology of H. horridum 2 and H. suspectum3, no direct comparison of the two has yet been made. 1 F. Day, "On some Irish G-asterostei," Journ. Linn. Soc, Zool. vol. xiii. 1878. 2 Troschel, F. II. De Helodermate horrido. Orat. in facult. phil. Bon-nensi. Bonn, 1851. Troschel, F. H. Arch. f. Nat. 1853, p. 294, pis. xiii. & xiv. Kaup, J. Arch. f. Nat. 1865, p 33, pi. iii. Gervais. P. Journ. de Zool. ii. 1873, p. 453, pi. xii. 3 Shufeldt, R. W . P. Z. S. 1890, p. 214, pis. xyii. & xviii. |