518 MB. R. LYBEKKER ON SOME [June 6, 



of imperfect) bones is frequently a matter of extreme difficulty, if 

 not of actual impossibility. 



Strix sancti-albani, n. sp. (Plate XLI. figs. 1-4.) 



In the British Museum Catalogue of Fossil Birds I took the 

 family Strvjidce to include all the members of the nocturnal birds 

 of prey, but I have since seen reason to adopt the subdivision of 

 the group into the families Strigidce and BubonidcB. And I am 

 the more confirmed in this latter view from the circumstance that 

 the specimens under consideration show an osteological distinction 

 between the members of those two families which I have not 

 observed recorded in the works with which I am familiar. 



Of all the birds represented in the collection the one of which 

 the remains are most numerous is a species of Owl belonging to 

 the genus Striv — no less than eleven more or less imperfect 

 bones being referable to this form. From these specimens I have 

 selected four for illustration (see Plate XLI.) — those represented 

 in figures 1 and 2 being the distal portions of the right tibia, 

 while those in figures 3 and 4 are respectively the proximal and 

 distal halves of the left tarso-metatarsus. The JStrigine affinities 

 of these specimens are amply demonstrated by the form of the 

 lower end of the tibia, in which the condyles are remarkably 

 prominent, while there is no bridge over the extensor groove on 

 the anterior aspect; and likeuise by the highly convex arch 

 formed by the distal trochlese of the tarso-metatarsus, and the 

 general form and prominence of the crest on the hinder part of 

 the hypotarsus. Although I am not aware that any sharply 

 defined distinction can be drawn between the tibia of the Buhonidfe 

 and StriffidcT, I find that Striv differs from all the members of the 

 former that I have been able to examine in the absence of the 

 bony bridge over the extensor depression of the upper part of the 

 anterior face of the tarso-metatarsus. As this bridge is wanting 

 in the specimens before us (fig. 3), and as they agree other\Aise in 

 general form and size with the corresponding bones of the Barn- 

 Owl, I opine that they must be referred to the genus StrLv. 

 Agreeing in size with the corresponding elements in S.flammea, 

 they are distinguished by the grooves between the distal condyles 

 of the tibia being somewhat less deep ; while the tarso-metatarsus 

 has a deeper posterior groove and a smaller crest to the hypotarsus. 

 The only fossil representative of the genus which, so far as I am 

 aware, has received a distinct name is ^S'. mclitensis^, founded on a 

 femur from the Pleistocene of Malta, which differs from that of 

 S. jlammea in its more slender proportions. As there are no 

 indications of a similar slenderness in the bones under considera- 

 tion, I think I shall be justified in assigning them to a new species, 

 under the name of S. sancti-cdhani. The specimens do not, 

 however, admit of defining the species more exactly than by the 

 above-mentioned features in which it differs from S. Jlammea. 



1 Lydekker, Cat. Foss. Birds Brit. Mus. p. 13 (1891). 



