Precaiidal Vertebra of Iclitlijosaurus australis. 145 



The posterior concave articular surface is infilled with 

 matrix, affording a complete cast of the next succeeding ante- 

 rior cup, and even retaining a portion of the osseous tissue of 

 the latter adhering to it. This tissue throughout the centrum 

 is well preserved and dense. 



The specimen is certainly of the Campjlodont group of 

 Ichthyosauri, and occupies an intermediate position in outline 

 between an " early posterior dorsal " and a " late posterior 

 dorsal " vertebra of /. trigonus, Owen *. 



The largest Ichthyosauri attained a length of from 30 to 

 40 feet, and the present meridianal species was in no way 

 inferior to its gigantic fellows of the European Secondary 

 seas. If we apply a similar method of arriving at the com- 

 parative size of an Ichthyosaurus as that adopted by Prof. Owen 

 — that the jaw was " thirteen times the length of the vertical 

 diameter of an abdominal or anterior caudal centrum " — we 

 see in the present fossil the representative of an animal 

 possessing a jaw a little over 5 feet in length — thus, 13 x 6" 

 = 65'' = 5' b" long. Prof. ]\[cCoy computed t the remains of 

 his type specimen to represent an animal 25 feet long. 

 Similar vertebra to tliat now described he states possessed a 

 diameter of 4 inches, and elsewhere he remarks \ that the 

 longitudinal measurement reached 1^ inch. The elastic 

 capsule was also preserved in some of his specimens. 



Mr. E. Lydekker, in the previously mentioned ' Catalogue,' 

 gives a list of species that "cannot be classified "§. Amongst 

 these are /. austrah's, McCoy, and /. marathonensi's, mihi. I 

 am afraid he has overlooked vSir Frederick's principal paper 

 on his I australis, wherein, although the description is meagre, 

 the latter specially compares the teeth of his fossil to those of 

 /. campylodon, and says they " have a rough bony square 

 base like those of /. campylodon (Carter)." As regards 

 /. marathonensis, mihi, less can perhaps be definitely said ; 

 but the wdiole of its structure, so far as we know it, is also 

 after the type of /. campylodon. In my paper on this fossil 

 I called attention to the necessity of affording another name 

 to /. australis, Hector, a New Zealand species distinct from 

 McCoy's. This has now been done by Mr. Lydekker 

 terming it /. Hectori || ; but unfortunately the species is of 

 no value, from the absence of either description or figure, all 



* Lydekker, Brit. Mu3. Cat. Foss. Reptilia and Amphibia, 18S9, pt. 2, 

 p. 26, tigs. 13 and 14. 



t Trans. Roy. Soc. Vict. ix. 2, 1869, p. 77. 

 X Ann. & Mag. Nat. Hist. (3) xix. 1867, p. 3.5'5. 

 § Loc. cit. p. Il3. 

 II Loc. cit. p. 113. 



