OCR Text |
Show 472 DR. W. G. RIDEWOOD ON THE CRANIAL [t)ec. 13, opercular. The palatine, ectopterygoid, and entopterygoid bear teeth. The ectopterygoid has an outwardly projecting ledge which serves to support the eyeball, and which comes into close relation with the upper edge of the middle of the three large bones of the suborbital series. The ectopterygoid is curved in the middle of its length, but not sharply bent. Opercular Series (text-figs. 131 and 132, pp. 470, 471).- The gill-cover is large, and the opercular and subopercular bones are of corresponding proportions. The branchiostegal rays are thirteen in number; eight of these are set on the outer side of the lower edge of the ceratohyal, and five on the epihyal. The shape is approximately the same in all, but the hinder ones are larger than those in front. Valenciennes (Hist. Nat. Poiss. xx. 1847, p. 469) and Gunther (Brit. Mus. Cat. Fish. vii. 1868, p. 466) put the number of branchiostegal rays as fifteen. Hyobranchial Series.-The lower hypohyal is slightly larger than the upper. The posterior one-third of the glossohyal cartilage is ossified; a narrow membrane-bone with a row of teeth along the middle covers the whole. The first, second, and third basibranchials are covered by separate membrane-bones, each bearing a narrow central row of teeth, but the investing lamina of the second basibranchial extends forward over the hinder part of the first basibranchial. The urohyal is long and slender. The fourth epibranchial is about as much expanded as in the Herring. The first pharyngobranchial is cartilaginous, and a spicular bone rises from the front end of the first epibranchial, and is attached by ligament to tlie pro-otic at the point marked s in text-fig. 130B, p. 469. E n g r a u l is e n cr a s ich o lu s . The cliondocranium of a young Anchovy of 25 mm. length has been described and figured by Pouchet (Journ. Anat. et Phys. 1878, p. 75, and figs. 49 and 50), but the account has no important bearing in the present connection. Cranium (text-fig. 133, p. 473).-The most remarkable feature about the general aspect of the cranium is the considerable vertical extent of the orbital region, a feature directly related to the large size of the eyes. The parietals are separated, and on the roof of the cranium is a pair of fontanelles, each bounded by the frontal, parietal, and supraoccipital. On the upper surface of each frontal bone are two cross bars or arches of bone, the anterior one strictly transverse, the second oblique. A distinct opisthotic is not present; the deep or opisthotic limb of the post-temporal is attached to a process of the exoccipital lying immediately over the foramen for the tenth nerve. The posterior temporal groove is shallow, and the temporal foramen, near its anterior end, is large and bounded by the frontal and parietal, with sometimes also a small portion of the squamosal below. Owing to the large size of the squamosal bulla that |