SPINED LOACH. 
707 
character also appears with considerable distinctness in 
the compressed form of the head, the thickness at the 
eyes being less than 2 / 5 of the length of the head", or 
than 3 / 4 of the length of the base of the dorsal tin''. 
The deep form of the snout is due to the marked de- 
velopment of the vertical plate of the ethmoid bone in 
front of the narrow frontal bones, which are arched 
above the orbits. The small round eyes are set high 
and turned somewhat upwards, above the more or less 
tumid cheeks, the distance between them and the upper 
protile of the forehead being about half their diameter 6 '. 
Their position is such that the length of the snout/ 7 
(from their anterior margin obliquely downwards to 
its tip) is less than the postorbital length of the 
head 6 (from the posterior margin of the eyes ob- 
liquely downwards to the hindmost part of the margin 
of the branehiostegal membrane). As in Misgurnus 
fossilis they are entirely covered with a thin skin 
( oculi velati, Bleeker), the orbits being externally de- 
stitute of any sharp limits. The anterior part of the 
orbits is coasted below by a longitudinal slit in the 
skin, out of which slit the fish can erect the preorbital 
spine, which otherwise points in a backward direction. 
This spine is formed, as Lilljeborg has pointed out, 
by the anterior frontal (lateral ethmoid) bone on each 
side. This circumstance may be most easily elucidated 
by a comparison with the following species, where the 
anterior frontal bone occupies exactly the same position 
as the extended (vertical) base of the spine in this spe- 
cies, forming the anterior margin of the orbit in a ver- 
tical position between the frontal and parasphenoid 
bones, but with a firm osseous connexion (suture) with 
the anterior outer margin of the orbitosphamoideum, 
which even separates the frontal bone proper from the 
upper anterior corner of the triangular anterior frontal 
bone. Here, in the Spined Loach, the said osseous 
connexion is loose and transformed into an articulation. 
r fhe bone is also of much harder texture, white and 
firm as dentine. Its base, which forms the long, ver- 
tical articulation with the orbitosphenoid bone, is almost 
terete and curved in a rounded obtuse angle, but is set 
in a somewhat oblique position, the lower (shorter) arm 
of the angle running obliquely inwards and forwards, 
while the upper arm is vertical. The tooth projects 
backwards in a direction approaching to that of the 
lower arm, at least below the middle of the basal part. 
It is curved backwards and inwards and is generally 
bicuspid, a shorter, but equally pointed tooth being set 
at the middle of the outer surface of the main tooth 7 . 
The base of the tooth is united by a strong ligament 
to the hind margin of the orbit. The suborbital bones 
seem otherwise to lie entirely wanting both in this spe- 
cies and Misgurnus fossilis. In front of the preorbital 
spine a dentiform protuberance belonging to the palatine 
bone may be felt beneath the skin, at the point where 
Fig. 176. Right preorbital spine of a Cobitis tcenia , seen from without. 
About 15 times the natural size. 
this bone is elongated in a backward direction to meet 
the entopterygoid bone. The nostrils are set rather high 
on the sides of the snout, somewhat nearer to the eyes 
than to the tip of the snout. The posterior nostril on 
each side is round and somewhat larger than the anterior, 
which lies just in front of it, and the hind superior 
margin of which is canaliculate or elevated in an obli- 
quely-cut, tubular form. The mouth is small and tooth- 
less; it lies on the under surface of the head, fringed 
by a comparatively thin upper lip, thickened only at 
the corners of the mouth, and small barbels, which 
comprise one pair in front and one on each side at the 
middle of the upper jaw, belonging to the dermal fold 
that runs from the cheeks over the mouth and forms 
the tip of the snout. The hindmost (largest) pair of 
barbels, on the other hand, lie at the corners of the 
“ 26 — 36 %, according to our measurements of specimens between 1 / 2 and 1 dm. long. The greatest thickness of the head measures, 
according to Canestrini, 27 — 40 % of its length in the typical Cobitis tcenia ; but in the form which has received the name of C. Icirvata , 
it is said sometimes to measure 47 *L % thereof. 
b 48 — 69 %, according to our measurements. 
c The diameter of the eyes is about 20 — 15 % of the length of the head. 
d About 38 — 43 % of the length of the head. 
e About 49 — 56 % of the length of the head. 
f G. C. CederstrOm (1. c.) has remarked as an external sexual difference that in the males the preorbital spine is furnished with 
several lateral denticulations. In the males examined by us, however, this character does not hold good. 
