Measurements. A B C mm. mm. mm. Total length 762 ([b]) 675 Length of rostrum 459 ... 427 Tip of beak to posterior end of pterygoids 561 ... 525 Height from vertex to end of pterygoids [c]292? 283 256 Breadth between orbits 327 [d]325 [d]287 Breadth between zygomatic processes 360 [e]325 302 Breadth at anteorbital notches 210 205 [f]182 Breadth of beak at middle 66 ... 60 Depth of beak at middle 54 ... 40 Greatest breadth of premaxillæ proximally 168 147 142 The same, in front of anterior nares 111 99 104 Breadth of anterior nares 51 45 42 Length of temporal fossæ 102 115 101 Breadth between temporal fossæ 228 212 208 Breadth of foramen magnum 42 34 34 Length of mandible 654 ... 565 Length of symphysis 135 ... 116 Greatest depth of mandible 120 ... 101 [a] Dimensions taken from Van Beneden and Gervais’ figures. [b] Beak lacking. Length from occipital condyles to base of beak (straight), 312 mm. [c] Pterygoids broken. [d] At middle. [e] Estimated. One zygoma is broken. [f] Least. VERTEBRÆ. The vertebral formula of three specimens of _M. bidens_ and of the Atlantic City specimen of _M. europæus_ is as follows: M. europæus. Atlantic City C. 7; Th. 9; L. 11; Ca. 20=47 M. bidens. Landenæs 7; 10; 11; 19=47 Fæø 7; 9; 11; 19=46 Udsire 7; 10; 9; 20=46 Although the skeleton of _M. europæus_ appears from the foregoing formula to include one less thoracic vertebra than those of _M. bidens_, as the last pair of ribs present is as long as the preceding ones, an additional pair probably existed originally. The formula for _europæus_ would then be: C. 7, Th. 10, L. 10, Ca. 20 = 47. (Pl. 13, fig. 1.)