THE SHOULDER-GIRDLE IN FISHES. 47 



however, the plate is elegantly four-lobed, and a considerable fissure passes forwards to the front 

 third. The middle bracluals would have been oval if their fission had been perfect ; but the upper- 

 most (b. 1) is almost triangular, and is notched in front, whilst the lowermost is somewhat lozenge- 

 shaped. The vertical rudimentary clefts are very small ; there is one notching the second and third, 

 and another the third and fourth ; they are nearer the posterior than the anterior margin. The 

 ectosteal plates have met each other through the centre of the ray, but further outwards they 

 are very thin, and enclose a thick core of soft cartilage, continuous with the common band in 

 front and with their own marginal band behind. By comparing this figure with fig. 12, 

 Plate II, it will be seen how near Cottus and Ambli/opus come to each other in the structure of 

 their Shoulder-plates. 



Example 2. Gobius minutus, Linn. 



The true Shoulder-girdle and Arm of the Little Goby are shown in Plate II, fig. 13, 

 magnified ten diameters. The proximal plate (sc., per. cr.) is a narrow band of partially 

 ossified cartilage, the unchanged part being nearly as long as the two ossifications taken together. 

 The bony scapula (sc.) is a peaked cap to this bar, the peak leaning backwards towards the 

 arrn-plate, and the base being pierced obliquely by the " scapular fenestra" (sc. f.). The 

 " glenoid" coraco-scapular belt (gl:) is rather thick, somewhat variable in breadth, and is widest 

 above and below, where it forms the soft core to the scapula and coracoid. This latter part (p. 

 cr., cr.) has its prse-coracoid region half the length of the coracoid proper ; they are nearly of the 

 same width, and meet at a very open angle ; the end of the coracoid is soft, and the cartilage 

 fills the conical cavity of the ectosteal coracoid. In front and behind there is an " inter- 

 clavicular wing ;" the hinder wing sends upwards the usual spur. At a short distance below the 

 coracoid, inside the grooved lower end of the clavicle, which is here indicated by dotted lines, 

 there is a flap of soft cartilage, in shape a high triangle, with rounded angles below ; this is 

 the epicoracoid (e. cr.) ; there has been but one transverse cleft, in this case, in the Shoulder- 

 girdle moiety. 



The brachial plate is one piece of hyaline cartilage, with four bone-plots marked out in it ; 

 and with two arrested vertical clefts ; these show the commencement of a division which, if perfect, 

 would have resulted in the formation of a post-brachial as well as a prse-brachial series. The 

 condition of this arm-plate, like the one in front of it, is very instructive ; it represents Amblyopus 

 in a much earlier stage of metamorphosis. In Plate II, fig. 14, a part of the middle transverse 

 cleft is shown, magnified 100 diameters. The transverse row of intervening cartilage-cells is 

 continuous ; its cells are only flattened, and are partly hidden by " ectosteal" teeth (sutural 

 serrations). At the lower left corner a patch of rounded cartilage-cells (c) is seen, showing that 

 the ectosteal plate is deficient here and there, and also that it has not touched the underlying 

 cells ; for the cells seen as scattered over the surface, and transversely spindle-shaped, are bone- 

 cells, formed in the ectosteal layer, altogether on the outside of the cartilaginous mass. Part of 

 one of the fenestra (f.) is seen, the rest being hidden by the sutural flaps : these flaps are very 

 common in the Fish-class, even when the ossification is incomplete; and these ectosteal growths 

 are wont to spread into the fibrous tissues much more readily than into the cartilage which 

 they invest ; they have both a centrifugal and a centripetal direction of growth ; but when the 

 bony deposit affects the intercellular substance of the hyaline cartilage, it becomes 



