THE SHOULDER-GIRDLE IN FISHES. 27 



The true essential Shoulder-girdle moiety is very small relatively to the great dermal plates 

 that outlie it (see fig. 12, sc. p. cr., cr.) ; but it is highly ossified, and partly anchylosed to the 

 dermal plates : moreover, its own three elements are to a considerable extent coalesced. The early 

 condition of the Shoulder-girdle of this Siluroid is persistent in the Trout and Herring (see 

 Plate II, figs. 4, 5, 7, 8) ; and in them the relations of the scapula (sc.), pre-coracoid (p. cr.), and 

 coracoid (cr.) are clearly shown. 



The three glenoid bosses (PI. I, fig. 11, gl. 1, 2, and 3) are arranged in a curved manner; 

 the upper looking forwards and outwards, the middle backwards, and the lowest backwards and 

 outwards : they articulate with the large, uppermost dentate ray (or spine) of the pectoral fin. 

 These oblong, convex condyles belong principally to the scapula (sc.), and they are partly 

 articulated with the three brachials, which are slightly displaced by the dermal ray, whilst the ray 

 itself articulates both with the scapula and the clavicle. There is a large "coraco-scapular 

 fenestra" (see fig. 12), and in front of it a smaller "scapular fenestra; " so that here, as in the 

 Skate (Raia), there is a scapular, a meso-scapular, and a prse-scapular bar. The prae-scapula 

 sends backwards a bony style, inside which the pointed prse-coracoid passes ; these two are 

 strongly tied together, to form the bony bar seen at p. cr. in fig. 12. There is a large 

 "coracoid foramen" (see fig. 2 A, c. fm.) at the root of the prse-coracoid (see fig. 12) ; it lies in 

 the angle of the " coracoid notch" (cr. n.) ; the main coracoid (cr.) is deeply grooved within, 

 it is almost anchylosed to the inter-clavicle, and ends in a point within and behind its last 

 sutural tooth. It must be remarked that the scapula is very low and broad, so that the 

 glenoid bosses lie obliquely behind its upper part : their high position arises from their relation 

 to the " pectoral dermal spine." Professor Huxley, in his invaluable ' Memoir on the Ganoids/ 

 pp. 34, 35, speaks of the inter-clavicle as "the so-called radius" (p. 35, fig. 21, d); but it has 

 nothing to do with Professor Owen's " radius," which is in reality the coracoid. (See Plate I, 

 fig. 14, cl. cr., for an easy explanation of the manner in which this mistake occurred; for the 

 coracoid of the Siluroids, as we have just seen, is anchylosed to the inside of the inter-clavicle, 

 but in fig. 14, which shows these plates in the Dory, the coracoid is exposed, having no inter- 

 clavicle outside it.) 



The Woodcut (fig. 2 A) will give a clearer idea of the structure and relations of the Shoulder 

 girdle and its splints in Callichthys than the figures in Plate I. This sketch represents the parts 

 as magnified four diameters, and the dermal bones are partly left in outline. The scapula 

 (sc.) is seen to rise but little above the glenoid bosses (gl., 1, 2, 3), and the manner in which the 

 scapula sends a style across to that of the pre-coracoid (p. cr.) is clearly shown; so also is the 

 coraco-scapular fenestra (c. s. f.), the scapular fenestra (s. f.), the coracoid foramen (c. fm.), and 

 the deeply grooved coracoid itself, strongly attached to the inter-clavicle (i. cl.), which hides it on 

 the outside. Above the scapula, part of the deeply scooped facet for the pectoral spine is seen in 

 the angular space of the clavicle (cl.). 



Example 2. Clarias capensis. 1 



Tor illustration of the Shoulder-girdle in this Siluroid I may refer, not only to the Wood- 

 cuts (figs. 2B, 2C), but also to Huxley and Hawkins's 'Atlas,' plate 11, figs. 11 a, \\b, and to the 



1 From a dissection of one of Professor Huxley's specimens from Congo, mentioned in his ' Memoir 

 on the Ganoids/ p. 33. 



