Descriptions and Records of Bees. 259 



The 1)0116 measures 45 cm. in extreme length, and its 

 form and pioportions are shown in the accompanying text- 

 figure. Its outer face is dense and smooth, as usual in the 

 carnivorous Dinosaurs; and there is a large internal cavity, 

 which lias caused its anterior wall to collapse and the upper 

 end to be twisted by crushing in the rock. The upper end 

 is expanded into the usual large cnemial crest (en.), but this 

 is distorted backwards and inwards. Tlie vertical ridge for 

 contact with the upper part of the fibula is similarly displaced. 

 The lower end, being more nearly solid, is better preserved, 

 and displays clearly the facette for tiio astragalus. Posteriorly 

 this facette (fig. A, fr.) is shown as a well-formed trochlea, 

 bounded externally by a low ridge (r.), which is also con- 

 spicuous in end-view (fig. C). Anteriorly the facette 

 (fig. B, a(/.) is produced upwards as a low triangular 

 depression, wliich would accommodate an ascending process 

 of the astragalus. Externally there is a large facette for 

 contact with the fibula (fig. B,fi.). 



Compared with the tibia of Megalosaurus'^ and ifs 

 immediate allies f, the new bone from the Lias is remarkably 

 slender. This slenderness, indeed, and the trochlear shape 

 of the facette for the astragalus, suggest a lighter and more 

 active reptile than the ordinary Megalosaurians. The great 

 develo|)ment of the anterior ascending process of the astra- 

 galus shows that the Liassic genus is more nearly related to 

 the Jurassic and Cretaceous than to the Triassic families of 

 carnivorous Dinosaurs ; but the tibia alone is insufficient for 

 a more exact determination of its affinities. 



XLIl. — Descriptions and Records of Bees. — XVI II. 

 By 'J\ D. A. COCKERELL, University of Colorado. 



Mecjacldh lielianihi^ sp. n. 



? .—Length V?)\ mm. 



Black, robust, but of the parallel-sided type ; ventral scopa 

 entirely white (in the type specimen full of bright orange 

 pollen) ; lower margin of clypeus strongly undulate, with a 

 broad, shallow, central emargination ; claws with a large and 



* R. Owen, ' Foss. Rept. Weald, .t Piirb. Form.' pt. iii. (Mon. Pal. 

 Soc. 1857), p. 18, pi. ix. 



t O. C. Mivrsh, ' The Diuosaiu's of North America ' (^l(Jth Ann. Hep. 

 U.S. (leol. 8urv. 1896), pp. 153-163, with plates. 



17-^ 



