CHAP. XL] HORNS. 285 



434-. Crateronyx dumi with five wings in the collection of WISKOTT in Breslau. 



435 Penthina salicella : left fore-wing about wider than the normal right fore- 



' wing. The apical border was markedly ernarginated, giving it a bilobed appearance. 



The nervures were as in the normal wing, except that the cells between the branches 



of the subcostal nervure were enlarged. ROGENHOFKH, ibid. [I am indebted to Dr 



Eogenhofer for a sketch of this specimen.] 



[Palloptera UStulata (Diptera): specimen having a large upright 

 scale on the thorax. This abnormal structure is like a third wing in 

 appearance, and is fixed on the thorax, passing from the head, back- 

 wards between the wings. Its upper border is circular, and in all 

 respects it resembles the upper wing-scale of one of the Calypterous 

 Muscidas. GERCKE, G., Wiener Ent. Ztg., 1886, v. p. 168.] 



HORNS OF SHEEP, GOATS AND DEER. 



436. Sheep. Repetition of the horns in sheep is well known. The 

 best account is that of H. VON NATHUSius 1 of which the following 

 is chiefly an abstract. 



Commonly there is a pair of extra horns placed externally to 

 the usual pair, but there may be three pairs in all, and even 

 higher numbers are recorded, though Nathusius had seen no such 

 case. The numbers on the two sides may be different, two on one 

 side and one on the other, and three on one side and two on the 

 other being sometimes met with. 



It is noticeable that in all cases the horns stand in a trans- 

 verse series, and not in a longitudinal series as they do in the 

 Four- horned Antelope (Tetraceros quadricornis). The bases of 

 the horn-cores are generally in contact, standing one outside the 

 other at the same transverse level on the skull. Nathusius 

 observed that in development the outgrowth for the horns of one 

 side is at first single, but afterwards divides into two or more 

 points, but he surmises that the division may appear earlier in 

 other cases. 



The external horns are generally smaller than the internal 

 ones, but this is not universal. In some cases of two pairs of 

 horns a small fifth horn is placed between the external and internal 

 horns of one side. 



In another form of double horn the horn-core of one side or 

 other may be a double structure, both cores being enclosed in a 

 single horn, which on being separated has a double-barrelled 

 appearance. 



Several examples of permanently four-horned breeds occur in 

 various localities, being described as common in Cyprus and 

 notably in Iceland and other northern islands. YOUATT (p. 169) 

 stated that there were two breeds of sheep in Iceland, the one 

 small and the other large, and that the greater part of both breeds 



1 H. VON NATHUSHJS, Vortr. lib. Viehzucht u. Rassenkenntniss, Th. n., Die ScJttif- 

 zucht, 1880, p. 177, fig. 47. 



