286 ALLEN: NEW ENGLAND WHALEBONE WHALES. 



of the tympanic bone are given as follows by Cope: axial length, 98 mm.; width at posterior 

 extremity of anterior hook at superior border, 71; width at anterior extremity of orifice, 35; 

 width at posterior extremity of orifice, 53; depth at middle (circa), 55; greatest depth of lip, 38. 



A well preserved centrum (Plate 15, fig. 10) from Gay Head, in the Society's collection 

 (no. 9698) is here referred provisionally to this species. It is probably a lumbar or a posterior 

 dorsal, and evidently belonged to an immature animal since the vertebral epiphyses had not 

 fused to the centrum and are lost. The face of the centrum is broadly elliptical; the neural 

 spine has been broken off except for a fragment of the base on each side between which the 

 superior part of the vertebra is flattened. The lateral processes are broken short off about 

 40 mm. from the body of the bone. They are broadly elliptical in section and rather stout 

 in proportion compared with the Common Finback, directed slightly downward. On the 

 ventral side of the centrum is a slight median keel, with a shallow depression on each side of it, 

 in the middle of which is a large perforation. The greatest length of this centrum is 145 mm.; 

 vertical diameter of centrum, 135 mm.; transverse diameter of centrum, 168 mm. 



In the collection of the Museum of Comparative Zoology are a number of centra from 

 Gay Head of various sizes and belonging evidently to at least three if not four different genera 

 of Cetacea. Among these are three caudal vertebrae, nearly complete, which are so like those 

 of the modern Balaenoptera as to be generically identical. The largest of these (M. C. Z. 

 8743; see Plate 15, figs. 1, 6) is nearly circular in outline and is evidently from the posterior 

 part of the peduncle. The epiphyses are fused to the body which indicates an adult animal. 

 Two foramina open into an elliptical pit in the center of the lower side, but the condition on the 

 upper side is obliterated. This bone measures : - 



Vertical diameter 110 mm. 



Transverse diameter 117 " 



Greatest fore-and-aft thickness 78 " 



Diameters of the ventral pit about 24X17 " 



The second vertebra (M. C. Z. 8742; Plate 15, figs. 2, 4, 7) is from a still more posterior posi- 

 tion and though essentially round, begins to show a rectangular outline, due to flattening from 

 above and below. The two foramina that penetrate it vertically open one at each end of a 

 long transverse groove which is bracket-shaped, and on the lower side come together in a shal- 

 low pit as in the first specimen. The bone measures : 



Vertical diameter 91 mm. 



Transverse diameter 96 " 



Greatest fore-and-aft thickness 67 " 



Diameters of the ventral pit about 25X26 " 



Transverse width of the dorsal groove. 64.5 " 



The third vertebra (M. C. Z. 3742; Plate 15, figs. 3, 5, 8) must have come from near the end 

 of the series, and is much more flattened, so that the outline is rectangular with rounded cor- 



