BIRD RECORDS FROM CALVERT FORMATION WETMORE 23 



Measurements.— TrunsxevsG diameter of shaft, 9.5 mm ; breadth of 

 distal end, 15.2 mm. 



Remarks.— A fossil gannet, Moris loxostyla (Cope), is known from 

 ihQ Miocene deposits of Calvert County, Md., but it is so much larger, 

 having the distal end of the humerus 21.1 mm,^ that it may be dis- 

 missed without detailed comment. Further, the species here de- 

 scribed seems related to the true boobies of the genus Sula, the 

 humerus of which differs from that of Moris in the more shortened 

 insertion for the pronator muscles and the broader radial condyle. 



In size Sula avita approaches S. pygmaea Milne Edwards * from 

 the lower Miocene deposits of Leognan (faluns de Saucats), France. 

 From the original description and figures it appears that S. pygmaea 

 is slightly smaller. Sida avita in addition differs in the conforma- 

 tion of the ectepicondylar area, which is larger, and also in the form 

 of the olecranal depression. S. pygmaea possibly is not properly 

 placed in the genus SvXa. 



Figure 2. — Type of Sula (Microsula) avita, new species : Lower end of humerus. About 



natural size. 



The type of jSula avita was the first specimen to come to hand, but 

 it has been followed by other fragments that are identified as from 

 this same species. Most important of these is a nearly complete left 

 metacarpal bone (U.S.N.M. no. 15158) collected by K. Lee Collins on 

 July 3, 1936, from zone 10 in the Calvert formation, 2 feet below the 

 top of the thick shell bed, at a point 1.1 miles south of Plumpoint, 

 Md. While apparently from a larger individual than the fragmen- 

 tary humerus taken as the type of avita, the proportionate difference 

 between the two is about that existing between male and female of 

 /S. piscator. 



The specimen (fig. 3) differs from Sula piscator in having the 

 projecting process of metacarpal I rising more abruptly, with the 

 entire process larger, and in the much smaller pneumatic foramina 

 on the proximal end, these being almost closed. Its form and char- 

 acters are shown in the accompanying drawings. 



There is also the shaft of a right humerus (U.S.N.M. no. 15157) 

 that is referred to this species. This specimen was found by R. Lee 



» See Wetmore, Auk, 1926, p. 468. 

 . «Bibl. ficole Hautes fitudes, vol. 11, art. 3, 1874, p. 8, pi. 12, fig. 2-23. 



