498 ' PROF. FLOWER ON THE DELPHlNIDjE. [NoV. 20, 



tion can be shown, in the same species. It is rather smaller than the 

 skull of D. marginata from Dieppe, measuring 436 millim. in length. 

 C. The next form of skull, with still narrower rostrum, is one 

 which is very abundant in all collections. It was first distinguished 

 from D. delphis by Cuvier (Annales du Museum, xix. 1812, p. 9) 

 under the name of i). dubius, with the following characters : — 

 " Smaller than D. delphis, with narrower rostrum, flat (not grooved) 

 below. Vomer showing itself for a small longitudinal space in the 

 middle, between the interniaxillaries and the maxillaries. Teeth 

 slender and pointed as in D. delpliis, 35 on each side of each jaw, 140 

 in all." In the series of skulls referable generally to this form in 

 the British Museum there are two distinct tyj)es, one called Glymenia 

 doris and the other Steno attenuatns. With the former must be 

 placed the solitary imperfect cranium of Delphhms clymene (Cat. 

 Cetacea B. M. 1850, p. 115)= C/ywewea nonH«fe (Synopsis), which 

 differs from the trne C. doris in having the teeth rather more numerous 

 (38) and more slender (only 2 millim. in diameter), and in the rostrum 

 being rather more depressed and the premaxilla less elevated above 

 the maxilla. There is a specimen like this in the Museum of the 

 Cambridge University ; and one, quite intermediate between it and 

 the typical C. doris, in the Museum of the College of Surgeons. With 

 Steno attenuatus must be included Steno capensis, Gray, not distin- 

 guishable from it. This must be a common form, judging by the num- 

 ber of craniamet with in collections, but unfortunately entire skeletons 

 are extremely rare. It certainly presents a distinct ap|)roach to the 

 typical Steno in the length and compression of the rostrum, the length 

 of the symphysis {\ to 1 of that of the ramus), and also the eleva- 

 tion of the anterior part of the infraorbital ridge, causing a distinct 

 depression between it and the raised outer edge of the premaxillae. 

 Dr. Gray says, in his ' Synopsis ' (p. 5), " This section is nearly in- 

 termediate between Steno and Clymenia." Though a single well- 

 marked specimen of Clymenia doris and of Steno attenuatus may be 

 so unlike as to justify their being placed as at least distinct species, it 

 is very remarkable that when a large series are compared together, as 

 those of the British Museum and College of Surgeons collections com- 

 bined, the two extremes pass so insensibly into each other that it is 

 impossible to say where one begins and the other ends ; and it is diffi- 

 cult to avoid the suspicion that the differences depend on age or sex, or 

 on individual variation, especially since we know how great the differ- 

 ences depending on these causes are in other better-known species. 

 A comparison of the skeletons of two of the extreme forms would 

 go far to clear up the difficulty. The size and form of the teeth is 

 much alike in all : they may be described as rather stout (being fully 

 3 millim. in diameter) compared with C. euphrosyne, obscura, or 

 longirostris ; but their numbers vary greatly, even in skulls other- 

 wise quite similar. As a general rule the broader skulls, or those 

 referable to Clymenia doris, have the smaller number, i. e. from 33 

 to 38, while the narrower forms (Steno attenuatus) have generally 

 as many as 38 or 40 on each side of each jaw. Very few of the 

 specimens of either form have localities assigned to them. 



