MR. R. LYDEKKER OX THE CETA.CEA OF THE SUFFOLK CRAO. 9 



angle, and the comparative lowness of the Eustachian portion of the 

 aperture agree with the existing Whales of the southern and tem- 

 perate oceans (B. biscayensis and B. australis). Yeiw great variation 

 in respect of certain details is found in this type of tympanic, the 

 difference between extreme examples being so great that if we had 

 only a few specimens to deal with, it would be necessary to refer 

 them to more than one species ; but in a large series it is found 

 that these variations apparently pass imperceptibly into one another, 

 and all the forms are therefore provisionally referred to one species, 

 which is B. primigenia of Van Beneden. In the typical form of 

 tympanic *, which we may call variety A, the inner wall is very 

 high, its superior border oblique, the flattening of the anterior sur- 

 face extending nearly or quite down to the border, the involucrum 

 considerably thickened, and the inferior border somewhat angulated. 

 There is a very perfect immature tympanic of this specimen in the 

 British Museum (No. 4:Q686), which was identified several years 

 ago by Prof. Van Beneden, and there are others in the Museum of 

 Practical Geology, and in the Ipswich Museum, and one fine example 

 in the Museum of the College of Surgeons (No. 2831). By the 

 courtesy of Mr. Colchester, of Ipswich, I figure (woodcut, fig. 1) a 



Fig. 1. — Bahena primigenia, Van Beneden, var. A, The imperfect 

 right tympanic ; from the Med Crag. Half nat. size. 



specimen of a right tympanic of this type, which has not been 

 subjected to rolling. In this specimen (of which a cast has been 

 taken by Mr. Colchester's permission for the British Museum) the 

 obliquity of the superior border of the inner wall is only moderate. 



In the form which may be called variety B, of which there is a 

 very fine example in the Museum of Practical Geology (PI. II. figs. 

 1, la), the obliquity of the superior border of the inner wall is 

 excessively developed, although most of the other characters are 



* See Van Beneden, Ann. Mus. R. Hist. Nat. Belg. vol. iv. pt. 2, pi. xix. figs. 

 1-4 and 9-12. 



