MARYLAND GEOLOGICAL SURVEY 59 



the Museum of the Academy [of] Natural Sciences, aided by the Oissaux 

 Fossiles of A. Mihie Edwards, I find it resembles closely the genus Sula. 



" The glenoid articular face descends to opposite the proximal third 

 of the length; it is transversely concave, and its inferior boundary is 

 raised to separate it from the longitudinal concavity which extends to 

 the head of the bone. A longitudinal angle separates this from the 

 interior part of the inferior face. The anterior extremity is curved 

 upwards and is thinned by a strong rabbett, which follows the convex 

 margin. This margin is slightly obtuse. The outline is abruptly con- 

 tracted below the glenoid surface. The inner outline is obtuse, and 

 without trace of the intermuscular ridge, on subclavicular ala. The 

 margin expands inwards to the distal articular extremity, remaining 

 almost equally obtuse. The distal extremity is far less expanded 

 towards the median line of sternum than in Sula bassana. It is also 

 everted, the outer (inferior) projecting border, being turned out (down) 

 from the line of the shaft. In Sula bassana this marginal rim appears, 

 from Edwards' plate, to be in the plane of the shaft. The articular 

 surface is divided by this rim into a narrow marginal external (inferior) 

 and a very much wider, strongly concave inner portion. The latter 

 is wider at the median end, where its inner (superior) margin is very 

 convex; it then contracts abruptly, leaving the remaining portion only 

 one-half as wide. The very slight prominence of the dividing angulate 

 projecting margin distinguishes this genus from Sula bassana. 



" There are three pneumatic foramina of no great size, in a short 

 series commencing just within the head of the bone. I am only able 

 to compare this bone with the figure of the same element of the Sula 

 bassana given by Edwards, as our museum does not possess a skeleton 

 referable to this genus. 



" As compared with the above, the glenoid articular face descends 

 more posteriorly (lower), and the superior (proximal) margin is more 

 transverse. The shaft viewed from before (below), contracts gradually 

 towards the distal expansion. The same contraction is visible when 

 viewed from the inner side. On the same view we observe that the 

 clavicular articulation is rather more posterior (lower down), and the 

 distal articular marginal edge is far less prominent and acute. The 



