or 99 mm. to the tips of the middle caudal rays. From 

 Ireland, ho\\ever, though the species is supposed lo 

 have been i)iaiitc(l there, Thomi'son uiciitions a si)eci- 

 nicii I) ill- (!■''- mill.) in length. The t'eniales attain 

 a wreatcr size than the males. In shoals of spawning 

 Minnows Heckkl and Kner found the length of the 

 females to vary between 92 and 10.5 mm., that of the 

 males hetweeii .J2 and 79 (exceptionally 92) mm. The 

 largest specimens in their possession were l."il mm. 

 long and came from Hungary. 



Tiie 1k)(I\- is elongated and of fairly uniform thick- 

 ness, the anterior part of the trunk showing so little 

 compression that tlie greatest thickness is at least '' ., 

 of the depth. Posteriorly the lines of the body con- 

 verge, as usual, even from the sides, but the tail is 

 still com])ai'ativclv terete. The depth of the head at 

 the occij)ut is slightly greater than its breadth. The 

 back is i)road and dejiressed in the median line into 

 a, groove, which may be exchanged in front of the 

 dorsal tin for a low carina. The belly is even and 

 terete, or, at the istlnnus, flat. The dorsal jirotile shows 

 a more or less distinct break at the occiput, but is 

 otherwise regular, like the ventral proiile, which differs 

 from that of the other Whitefishes in being free from 

 any perceptible break, even at the vent or along the 

 anal fin. 



The most characteristic point in the form of the 

 head consists of a swelling (thickening of the ethmoid 

 bone) on the snout between the nostrils. The occiput 

 and forehead are slightly convex or (especially the 

 latter) nearly flat; the gill-covers and cheeks almost 

 perpendicular. The eyes are middle-sized and set so 

 high th;it their superior margin lies almost in the same 

 plane as the forehead. Their longitudinal diameter 

 measures in young specimens (' ^ dm. long) about 30 

 %, in average-sized specimens about 28 %, and in spe- 

 cimens 1 dm. long about 23 %, of the length of the 

 head; the vertical diameter is ''/\„ — ■* - of the longi- 

 tudinal. They lie almost entirely in the anterior half 

 of the head, the postorbital length of the latter being- 

 only slightly less than the length of the snout and the 

 eye togetiier. Tiu' breadth of the interorbital space is 

 always greater than the diameter of the eyes and va- 

 ries between 40 and 80 % of the length of tiie head. 

 The horizontal profile of the snout is obtusely (slightly) 

 rounded, and its tip generally projects a little beyond 

 that o{' the lower jaw. The cleft of the moutii, with 

 its flesiiy lips, is small and turned slightly upwards. 



The length of the iip]K'i' jaw from the middle of the 

 ti[) of the snout is, as a rule, erjual to that of the 

 snout, or about 30 % of that of the iiead. The lengtii 

 of the lower jaw is about the same as the breadth of 

 the interorbital space, or on an average ' 3 of the length 

 of the head. The; nostrils are round and rather large, 

 but set close together, the posterior nostril being usu- 

 ally covered to a great (extent by the dermal flaji that 

 rises from the narrow bridge between them. They lie 

 much nearer to the eyes thiin to the tip of the snout. 

 The gill-openings are comparatively large, extending 

 above along about half the upper margin of the gill- 

 cover, and separated at the isthnnis l)y a distance some- 

 times scarcely half the diameter of the e3'es. The 

 branchiostegal rays as well as the rim outside them are 

 broad. The gill-rakers are small; in the outer row on 

 the first branchial arch they are about 8 in number, 

 scattered, verrucose, and liardh distinguishable. The 

 pharyngeal teeth show considerable variation in number. 

 In most cases they are set in t\vo rows, the large roNv 

 on the inside of the lower arm of the bones generally 

 containing 5 teeth on th<; left side and 4 on the right, 

 and the smaller row, outside the former one, consist- 

 ing of 2 small, almost cylindrical teeth. Sometimes, 

 however, not a trace of this smaller row can be found. 

 We have never found the ]iharyngeal cartilage present: 

 according to Fatio it is of an obtuse heart-shape, with 

 the posterior part attached like a knob to the anterior. 

 Our figure (fig. 188, c) shows, on the other hand, 

 how the mucous memlirane of the pharynx covers the 

 downward process of the occipital bone at the spot 

 where the pharyngeal cartilage is otherwise developed. 

 This figure may also assist in the explanation of the 

 form possessed by the pharyngeal cartilage in the ma- 

 jority of the following Leuciscines, at least in the larger 

 ones. The surface of this cartilage is heart-shaped. 

 On each side of it the roof of the phar3-nx shows deep 

 hollows, converging in a forward and upward direction 

 (downward in the figure, which is drawn from a spe- 

 cimen laid on its back, with the head turned towards 

 the artist). But at the middle of the base of this 

 heart-shape the mucous membrane is continued (u]i- 

 ward in the figure) in a rounded (convex) coat over 

 the lower (posterior) part of the said occipital process, 

 until it leaves this process and passes into the upper 

 wall of the oesophagus. This convex part forms the 

 foundation of the callosity which, especially in the 

 larger Whitefishes (see, for example, the C'huli. fig. 



