MINOR ABNORMALITIES PUG-HEAD 49 



Other Fishes: 



Examples in Cyprinus are furnished by Knauthe (1*25-6), Lowne (146 P- 55), Otto (178 

 thirteen instances), St. Hilaire (213 PI. I. figs. 4-6), Tornier (350) ; in Abramis vimba by Leon- 

 hardt (140) ; in Esox by Otto (178), and Vrolik (266); in Anguilla by Lowne (146 p. 55), and 

 Tornier (250); in Lumpenus by Pappenheim (183); in Perca by Pellegrin (189); in Mitgil chelo, 

 M. capita, Gobius ophiocephalus, Labrax lupus, Gadus minutus, Pleuronectes italicus, Merluccius vulgaris, 

 by Ninni (1 68) ; in Cottus by Nystrom (1 74), and in Mugil capita by Canestrini (35). Leonhardt 

 (140) refers to records in Cyprinus by Neydeck, Steindachner, and Hofer; in Lumpenus lampetrae- 

 formis, Gadus mcrlangus, G. morrhua, and an eel, by Lonneberg ; and in Salmo irideus and Esox 

 Indus by Hofer. Freund (70) gives a record, having reference to Phoxinus laevis. 



In typical examples the snout is markedly reduced in size, and curved in such a way that the 

 anterior frontal region arches rapidly downwards just in front of the eyes. The latter are lessened 

 in horizontal diameter and become oval in shape, having the long axis vertical. The lower jaw 

 retains its usual size, and accordingly projects a considerable distance in front of the rest of the 

 head. The incurving of the tip of the snout may be so great that what should be its dorsal surface 

 comes to look downwards into the floor of the mouth. The deformity varies greatly in amount in 

 different specimens, and also passes without very abrupt separation into the " round-head " condition 

 to be afterwards described (p. 50). 



Skeleton. The skull is practically normal as far forward as the anterior border of the eyes. 

 In front of this region the usual skeletal elements tend to occur, but they are reduced in size, 

 altered in shape, and curved downwards, while still retaining as far as possible their ordinary 

 connections with one another. In the region affected, the axial stem of the skull consists of vomer 

 and parasphenoid. Sometimes the stem suffers simple shortening, below and in front of the eyes, 

 and sometimes, in addition to being shortened, it becomes sharply bent on itself in this region, so as 

 to form a V, the apex of which points upwards. These two varieties are connected by inter- 

 mediate forms. 



The frontals curve downwards so that the mesethmoid lies below instead of anterior to them ; 

 the lateral ethmoids and the nasals are similarly displaced, while the premaxillaries are so far curved 

 round that they lie behind instead of anterior to the mesethmoid. 



The intermaxillary and maxillary are smaller, and carry fewer teeth, than in the normal 

 condition. Thus the former has two teeth in the instance described by Tornier (S50), and four in 

 that described by Lidth de Jeude (114), the normal number being about six. In an excellent 

 example from the eel, Tornier (250 p. 307) notes that neither the pterygoids nor the maxillaries 

 nor the vomer are provided with teeth, while all these bones have many rows of teeth in the normal 

 condition. The shortened maxillaries lie transversely, or, in extreme cases, are directed backwards. 

 The skeletal elements which go to form the anterior or palato-pterygoid limb of the suspensorial arch 

 are smaller than normal, particularly those near the ethmo-palatine extremity of the limb, where, 

 indeed, some of them may be no longer recognisable. On the other hand, those which form the 

 posterior (hyomandibular-quadrate) limb of the arch in question tend to be of normal size. 



A number of these points are brought out in the following description from Carlet (36 Salmo). 

 The frontals curve downwards at the level of their orbital processes. The mesethmoid lies below 

 the frontals. The lateral ethmoids and the openings of the nostrils are also displaced downwards. 

 The pterygo-palatine is reduced in length, but the shortening affects the ento- and ecto-pterygoids less 

 than the palatines, which are short and almost transverse. The vomer is slightly shortened, and the 

 parasphenoid is very short, especially in its anterior part. The orbito- and ali-sphenoids are similarly 

 reduced in length. The descriptions by Hofer (96a) and Freund (70) may also be consulted. 



Leonhardt (140) gives a careful series of measurements of different parts of the head 

 in his Abramis vimba specimens, together with a fairly complete account of their osteology. 



Mention should be made of an example from the eel in the Eoyal College of Surgeons' 

 Museum (Lowne 146 p. 55). The mandibular extends forwards beyond the anterior extremity 



