THE SHOULDER-GIRDLE IN FISHES. 17 



The coraco-scapular plate is entirely unossified, as in Amia and the Lophobranchii, and it 

 has no " fenestra " (fig. 1 C, sc. cr.) : there is, however, an ovoidal scooped space on the inner 

 side. The scapular region (sc.) is pointed above, in front ; behind, it forms a thick, cleft boss 

 the glenoid elevation and depression : below this part it gradually becomes narrower ; has sinuate 

 edges, both before and behind ; and ends below in a broad three-toothed oblique margin, which is 

 very thin. The arm-plate, altogether, is oval, with the broad end behind ; its first moiety is partially 

 subdivided into three rays prse-brachials (see fig. 1 C, p. b. 1 3). The upper and lower 

 prse-brachial rays are long sigmoid rods, soft at the ends, continuous proximally, the lower being 

 the longest by one-fourth. Between these rays there is a large, pointed, oval leaf of thin clear 

 cartilage, it is continuous with the upper ray, distally, which is lobulate where it runs into 

 the leafy plate. At a little distance from the evenly semicircular posterior end of this flat 

 middle prae-brachial (p. b. 2) there is a second crescentic row of post-brachial rays, thirteen in 

 number (fig. 1 C, pt. b.). The two uppermost are unossified, as also is the lowest; the other 

 ten are drumstick-like, with large soft ends projecting from the thin ectosteal sheaths : the 

 distal ends are almost globular, the proximal oblongo-oval. 



The uppermost post-brachial ray is obliquely spatulate, the second thicker than the ossified 

 rays, but approaches them in form ; the lowest is a low triangle, with its base upwards. Here, if 

 anywhere, we have an instructive morphological condition ; it has cost much labour to make 

 it out thoroughly, but alkalies and glycerine have made the whole of this delicate " arm " 

 translucent, and patience has done the rest. 1 



Example 3. Lcpidosteus lucius, Owen. 



The skeleton of this Fish (see ' Osteol. Catal. Mus. Coll. Surg.,' vol. i, p. 82, No. 369) is 

 well worth careful study, as it shows a still greater approach to the typical structure. 



In Huxley and Hawkins's ' Atlas ' (plate 5, fig. 2) there is a side view of the skull ; but 

 only one of the bones to be described by me is seen in this figure. This is the " post-temporal " 

 a pistol-shaped bone, the hinder of the two lying above the operculum (op.) ; it is a strong, thick 

 ganoid plate, articulating with the ganoid roof-bones above and with the supra-temporals in 

 front. The " stock " of this bone is its smooth, rounded, lower end, which fits into a cup on 

 the outside of the top of a strong subcutaneous, sickle-shaped " supra-clavicle." This latter bone 

 in its turn overlaps the large, long, lunate clavicle, which, passing downwards and forwards, 

 meets its fellow at the mid-line without the intervention of the " inter-clavicular " pieces. The 

 post-clavicles may be pitched upon amongst the next succeeding dermal bones, but they have 

 very little specialisation. Here we have arrived at the typical condition of the supra-clavicle and 

 the clavicle ; but the post-temporal is still very little like that of ordinary Teleostei. 



Example 4. Amia calva, Linn. 



In this living Ganoid there is much correspondence with Lepidosteus in the bony plates 



1 I should wrong my friend Mr. T. J. Moore, of Liverpool, if I were to omit to mention that 

 he it was who pointed out to me the paper by Dr. J. A. Smith in the ' Annals of Nat. Hist. ;' and, 

 still better, where actual specimens could be procured, namely, from Mr. Gerrard, Jun. 

 3 



