Stewart.] Cretaceous Fishes. 285 



somewhat wing-like, anterior portion, whose entire structure is 

 not known. In the median line the two halves are strongly 

 united together by suture, and at the point of union there is a 

 prominent swelling of the bone all around. There are four 

 facets on each for the fin attachment. The upper and lower 

 are large, flat facets, somewhat ovoid in outline, and support 

 the upper and lower halves of the first ventral fin-ray. When 

 seen in cross- section from behind they are obliquely set, but 

 hardly so much so as in IeJitlnjodectes. The lower one of these 

 facets is the larger, and has two more facets between this and 

 the upper, of a somewhat tubercular nature. The last two are 

 for succeeding rays or basiosts. In front of the articular por- 

 tion the bone becomes thin and somewhat expanded. On the 

 outer border of this portion there is a prominent crest both 

 above and below, of which the upper is the larger. It is likely 

 that this crest did not extend very far forward, but was prob- 

 ably succeeded in front by another smaller crest or tuberosity, 

 as something of the kind is shown in the figure of this part by 

 Professor Hay, 50 but not described in the text. On the internal 

 border there is a prominent ridge of bone extending forward on 

 both the superior and inferior surfaces. These two ridges 

 nearly coincide with each other, thus forming a rod of bone, 

 which extends forward, but how far is not known. These two 

 bars are separated by quite an interval, as is shown in the cut. 

 There seems to be some difference between this specimen and 

 the one figured by Professor Hay. In his specimen the distance 

 across the external crests was probably about 15 cm., and the 

 distance between the internal ridges about 4.8 cm. In our speci- 

 men the first of these measurements is 12.3 cm.,"' 1 while the last 

 is 5 cm., making the distance between those ridges proportion- 

 ally greater in our specimen. 



Distance across superior facets 83 mm. 



Distance across inferior facets 52 " 



Distance across middle facets 80 " 



Vertical depth of articular portion 52 " 



There are none of the pelvic tin-rays present, but they were 



50. Zool. Bull. 1868, p. 41. 



51. Approxima 1 



