ON A SPINAL COLUMN OP LOXOMMA ALLMANNI. 351 



On looking along the spine there is an appearance of alterna- 

 tion of large and small vertebral bodies, which is owing to the 

 alternate succession of centra and intervertebral disks ; these 

 latter, being less firm and solid during life, have shrunk more 

 after death than the former. 



In Mr. Barkas' "Gruide" above mentioned, the disks had 

 been counted as vertebral centres, and in the paper by the late 

 Mr. Atthey and myself, " On the Skull and other Bones of 

 Loxomma AUmanni, Huxley," in Yol. Y. of the Natural History 

 Transactions of Northumberland and Durham, p. 219, it is 

 stated, that "the centra of the vertebrse are commonly of con- 

 siderable size, alternately large and small." Both this statement 

 and Mr. Barkas' counting are erroneous, the appearance of al- 

 ternation being caused as above stated. 



The skull, and an unknown number of vertebrse at each end 

 of both fragments, also the sternum and by far the greater part 

 of the ribs, with the thoracic and pelvic girdles, and their limbs 

 (if such existed) are absent. It is therefore a difficult matter to 

 estimate the length and bulk of such a creature, which must 

 have been an adult. 



In the first place, we know that the total length of the two 

 fragments under consideration is four feet seven and a half inches. 

 In the next place, allowance must be made for the length of the 

 absent parts. From what we know of skulls of Loxomma in 

 our Museums and elsewhere, we may safely take the length of 

 the cranium to have been fourteen inches. For the length of 

 absent vertebrae, which should connect the anterior end of our 

 longer fragment with the occiput, we assume it to have been 

 four or five inches. For absent vertebrse, to fill up the gap be- 

 tween our two fragments, we allow six or more inches. For 

 vertebrse wanting at the posterior end of the lesser fragment, 

 including the caudal extremity, not less than six or even seven 

 feet — the tails of modern amphibians, crocodiles and alligators 

 being fully as long as, or even longer than, the body and head 

 together. Lastly, for shrinking during the decomposition and 

 fossilization of the body, we allow two inches. Thus, 4 ft. 1 |-in. - 

 -i- 6in. -f 1ft. 2 in. + 5 in. 4- 6 in. + 6 ft. 10 in. -|- 2in. = 



