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 ^ 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 

 devfloped. The abnormal Bream has been placed in the Museum 

 of the Royal College of Surgeons. 



DESCEIPTTON OF PLATE X. 

 Fig. 1. Specimen without pelvic fins. 

 Fig. 2. Outline of normal fish. 

 Fig. 3. Ventral view of pelvic girdle and iins of 2. 



5. Notes ou the Osteology of Heloderma horrklum and H. sus- 

 pectum, with Remarks on the Systematic Position of the 

 Heloclermatidce and on the Vertebrse 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 ^ and H. sus- 

 pectufn ^, no direct comparison of the two has yet been made. 



1 F. Day, "On some Irish Gasterostei," Journ. Linn. Soc, Zool. vol. xiii. 

 1878. 



^ Ti-oschel, F. H. Ue Helodermate horrido. Orat. in facult. phil. Eon- 



nensi. Bonn, 185L 

 . Troschel, F. H. Arch. f. Nat. 18.53, p. 294, pis. xiii. & xiv. 

 Kaup, J. Arch. f. Nat. 186.5, p 33, pi. iii. 

 Gervais, P. Journ. de Zool. ii. 1873, p. 4.53. pi. xii. 

 = Shufeldt, n. W. P. Z. S. 1890, p. 214, pis. xvii. &. xviii. 



