BRITISH FOSSIL CRETACEOUS BIRDS. 503 



comprises portions of three vertebrae — one entire in the middle, and a 

 fractured vertebra at each end. In general form the vertebrae rather 

 recall the middle sacral region of Penguins. The centrum is rather 

 more than -| inch long, while the least width at the intervertebral fora- 

 men is y^ inch. The sides, concave in length, are compressed so as to 

 converge inferiorly in a rounded median keel. The vertebral fora- 

 mina are large, rounded, and placed behind the transverse process 

 just at the hindermost part of the centrum (fig. 16). The neural plat- 

 form is wide, horizontal, and imperfectly preserved ; it is traversed 

 in the median line by a low neural spine aboutyL-inch high and as wide. 

 The depth from the neural spine to the base of the centrum is fully 

 T ?g- inch. The substance of the centrum is largely excavated for the 

 neural canal, which is cylindrical and £ inch in diameter. The 

 position of the transverse processes is above the middle of the neural 

 canal. Both the specimens described are from the part of the sacrum 

 anterior to the femoral articulation in the pelvis. 



The third specimen (figs. 17, 18, 19) is postfemoral ; it has almost 

 exactly the form of the region immediately postfemoral in the Diver. 

 It comprises portions of four vertebrae perfectly ankylosed together. 

 In transverse section the mass is triangular (fig. 17), having the base 

 flattened ; and the flattened sides converge dorsally to a sharp ridge, 

 with which the iliac bones were in contact. The specimen is 1 ^ inch 

 long, T ^ inch high as preserved anteriorly, and about ^ inch high 

 posteriorly. The base (fig. 18), which is channeDed in length as in the 

 Diver, is margined on each side by a subangular ridge, external to which 

 is a narrow flattened lateral area which looks downward and out- 

 ward. The width of a centrum in front, where narrowest between 

 the transverse processes, is less than f inch ; posteriorly the sacrum 

 becomes steadily narrower. On the lower portion of the lateral 

 aspect (fig. 10) is a row of four large rounded intervertebral foramina, 

 less than g inch in diameter, between which are the eminences forming 

 the bases of the short transverse processes. The flat side above 

 these foramina and processes, -f^ inch deep, is divided into rhomboid 

 areas by impressed lines running upward and backward at unequal 

 distances from each other. Posteriorly at the fracture the sacrum 

 is becoming greatly compressed ; but there is no means of estimating 

 the number of vertebrae iu the posterior missing portion. In the 

 Diver there are six vertebrae posterior to the corresponding sacral 

 region ; but if Enaliomis had a long tail, the sacrum may have in- 

 cluded fewer postfemoral elements. 



Caudal Vertebra*. (PI. XXVI. figs. 20, 21, 22.) 



Two small vertebrae, apparently caudal and procoelous, I am in- 

 clined to assign to the caudal region of Enaliomis ; if so, they are 

 separate elements of the ploughshare bone, and would indicate a 

 peculiar condition of the termination of the tail. The centrum is 

 compressed from side to side ; and the neural arch, which hangs for- 

 ward a good deal (fig. 20), shares in the compression. The centrum is 

 about ^ inch deep, and -^ inch in width superiorly, where it is widest ; 



