ME. R. LYDEKKER ON THE CETACEA OF THE SUFFOLK CRAG. ll 



I cannot but adopt such species*. In regard, however, to the 

 names applied to two of these species, it is necessary to replace 

 those given by Prof. Yan Beneden by the earlier Owenian ones. 

 It may be added that the great number of species in this section 

 renders the specific determination of detached vertebrae in many 

 instances a matter of great difficulty and uncertainty ; and it may 

 also be mentioned that owing to the more fragile nature of the 

 outer wall of the tympanic in the Rorquals, fairly perfect specimens 

 of these bones are much less common in the Eed Crag than in the 

 case of the Right Whales. 



In the genus Megaptera (in which the t}Tnpanic is more inflated 

 and its involucrum more pear-shaped than in Balcmoptera) we may, 

 I think, certainly include the genus Burtinopsis of Yan Beneden, 

 which has been described as intermediate between Megaptera and 

 Balcenoptera, although the tympanies figured by Yan Beneden f are 

 undistinguishable in structure from those of Megaptera hoops. To 

 Megaptera affinis, Yan Beneden, I provisionally refer an immature 

 right tympanic (PL II. figs. 4, 4 a) from the Coralline Crag, which 

 is preserved in the Museum of Practical Geology, and in its blunted 

 anterior extremity agrees very closely with the larger example 

 figured by Yan Beneden in the Ann. Mus. R. Hist. Nat. Belg. 

 vol. vii. pt. 3, pi. xliii. figs. 1, 2. 



A left periotic, from the Red Crag, in the British Museum (No. 

 39020), from the narrow and elongated form of the portion containing 

 the semicircular canals, evidently belongs to the present genus (as 

 distinct from Balcmoptera and Cetoilieriuni) ; and as it is apparently 

 adult, and much smaller than the corresponding bone of M. affinis 

 figured by Yan Beneden in the Ann. Mus. R. Hist. Nat. Belg. 

 vol. vii. pt. 3, pi. xlii. fig. 4, and is apparently too large for M. 

 (Burtinopisis) minuta, Yan Beneden, the probability is that it belongs 

 to the somewhat larger M. {Burtinopsis) similis, Yan Beneden. 

 The small M. minuta is represented by a nearly perfect left tympanic 

 (PI. II. figs. 5, 5 a) from the Coralline Crag, which is preserved in 

 the Ipswich Museum, and agrees exactly with the tympanic figured 

 by Yan Beneden, op. cit. pi. xcvii. figs. 9—11, under the name of 

 Burtinopsis. Except by its smaller size, the English specimen can 

 scarcely be distinguished from the tympanic of the existing M. hoops. 



To the genus Balcmoptera belongs the so-called Balcena definitely 

 Owen, of which there is a fairly perfect tympanic in the Ipswich 

 Museum (PL II. figs. 3, 3 a). This specimen agrees exactly with 

 the imperfect type tympanic (of which a cast is preserved in the 

 Museum of the College of Surgeons %) ; and as it differs from the 

 corresponding bone of B. Goropi, Yan Beneden, by its larger size, its 



* In many instances'it does not appear to me by any means certain that the 

 vertebrae belong to the same species as the tympanies, and it is therefore advisable 

 to regard the latter as the types of such species. 



t Ann. Mus. ~R. Hist. Nat. Belg. vol. vii. pt. 3, pis. lxxxix. & xcvii. The 

 recent tympanic figured in pi. lxxxix. figs. 15, 16, under the name of Balcenoptera 

 antarctica, certainly belongs to Megcqrfera hoops, and might have been drawn 

 from a specimen in the British Museum (No. 2.76.16.18). 



X Nos. 2805 aud 2832 in the same collection belong to this species. 



