506 
It would be a great boon if Prof. McCoy would publish a full description of this 
interesting Reptile, as quite recently fine additional remains of I. australis have come to 
hand through the labours of Messrs. J. Burkitt, J. Hugh Moor, and L. Mackinnon. 
The first of these gentlemen has obtained the snout portion of a large head with powerful 
teeth and a number of united vertebr® ; the second a portion of a skull showing the 
orbit, with sclerotic plates in situ, and a largo number of disjointed centrums of vertebrae ; 
whilst the last-named collector has forwarded other disarticulated centrums, which, 
although smaller, have every appearance of being those of this species. 
Loe. Base of Walker’s Table Mountain, Flinders River {Messrs. Carson and 
Sutherland — Nat. Mus., Melbourne) ; Bed of Flinders River, thirty-five miles below 
Richmond Downs, aqjproximately Lat. 20° 37’ S., Long. 142° 43' E. {J. BurMtf) ; 
Flinders River, at Manfred Downs, approximately Lat. 20° 5' 8., Long. 141° 45' E. 
(Ji Hugh Moor') ; Glendower, Upper Flinders {W. L. MacTcinnon). 
ICHTHXOSAUEUS MARATHONENSis, Etheridge Jil. 
Ichth!/osau7-us marathonensis, Eth. fit, l^roo. Linn. Soe. N. S. Wales, 1888, iii., Pt. 2, ii. 405, t. 7. 
Obs. The fossil consists of that part of the upper and lower jaws of a large skull 
anterior to the nostrils. It measures ten inches in length, and exhibits the greater 
portion of the right maxillary and deutary bones, and a portion of the left. At the 
anterior end the specimen has been broken off short, immediately posterior to the union 
of the rami, and at the hinder end just anterior to the outer termination of the nasal 
bones. At the former the snout is three and a-half to four inches in transverse measure- 
ment, and at the latter point four and a-lialf iuches. There are thirty teeth in all 
preserved, ten implanted in the pre-maxillary, and eleven in the dentary. 
Both bones are longitudinally channelled by a deep semi-interrupted groove, 
similar to that seen in other species of Ichthyosaurus. 
The teeth are of medium size, but larger than in some species, measuring from an 
inch to an inch and a-quartcr from the alveolar edge to the apex of the crown, but 
including the implanted base, one of the foremost teeth measures an inch and three- 
quarters in length. They increase in diameter and stoutness from before backwards, are 
conical sub-circular in section, with a non-tronchant and apparently straight crown. The 
enamel is ornamented with grooves and ridges, but there is no evidence that the cronm 
apices were devoid of these ; but, on the contrary, the upper portions of the crown and 
the base of the teeth above the alveolus appear to be more strongly ridged than does the 
middle line of each tooth. In the' most anterior tooth but one preserved in the 
pre-maxillary, having a sectional diameter of half an inch, there is a pulp cavity of 
three-sixteenths of an inch. 
In a transverse section of the posterior end the following facts are discernible. 
The breadth of the pi-e-maxillary across the top of the alveolar cavity is one inch. On 
the outer border the external groove traversing this bone longitudinally leads into a 
well-marked cavity, the exterior alveolar wall being thin, but this is perhaps owing to 
some extent to the lateral abrasion the specimen has undergone. The alveolus cut by 
the section is five-eighths of an inch wide and an inch in depth. From the thickened 
and enlarged lower end the inner wall of the bone is directed upwards in a fairly 
straight line until it reaches a point on a level with the upper end of the alveolus. Here 
it takes a well-marked bend inwards to above the cavity of the external gro'ove ; thence 
it bends outwards to become the median surface for union with that of the left pre- 
maxillary. The inner alveolar wall descends at least four-eighths of an inch lower than 
the outer one. There is no indication of the nasals. In the lower jaw the lower portion 
of the dentary is not preserved, having flaked off from the specimen, but this bone 
