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Appendices to Fifth Annual Repoft 



end rod-like and lying in the closed month (PI. XVIL fig. 15, jug.) parallel 

 and dorsal to the maxilla; in the open month it stands nearly directly up- 

 wards (PI. XV. fig. 1, jug.), surrounded only by muscle and connective tissue. 

 Its posterior part, which overlaps and is closely attached to the maxilla, is 

 expanded into a flat oval form. Filling the narrow interval, and between 

 the rod-like portion of the jugal and the posterior edge of the maxilla, and 

 extending upwards to near its upper angle, is a narrow splint-like bone. 

 This, I believe, is the septo-maxillary of Parker, * but its appearance and 

 position in the herring (it is fully developed in the 30 mm. herring) exter- 

 nal to and separated entirely from the normal septo-maxillary position 

 causes me to doubt its homology with that bone in other vertebrates. 

 Dorsal to its upper end, and intervening between the nasal cavity and it, 

 is a small bone forming part of the orbital circle, but it is peculiar, in so 

 far as while its flattened posterior end is overlapped by a narrow elongated 

 supraorbital lying along the edge of the frontal and extending backwards 

 nearly over the whole eye, and while it is closely connected by its narrow 

 rod-like anterior end with the suborbital (lachrymal) covering the antorbital 

 cavity, it articulates, and is firmly attached by a slightly nodular head to 

 the premaxilla. This bone forms partially the outer side of the nasal 

 cavity. There are two strong crescentic sclerotic ossifications (oc. os.). 



The suborbitals are five in number. Immediately beneath the eye, and 

 forming a large flat surface on the side of the face, overlapping the 

 preoperculum, is the largest of the series (PI. XVIL fig. 15, S). Its upper 

 edge curved for the eye, it descends as far as the level of the closed lower 

 jaw, its anterior end being slightly sunk to receive the circular end of the 

 maxilla and jugal when closed ; its upper anterior portion therefore pro- 

 jects forwards, to be overlapped by a short narrow second suborbital 

 (fig. 15, 2), which in turn is overlapped by the anterior of the series 

 the lachrymal (fig. 15, 1), and which is above referred to. Second in 

 width of these bones, its anterior end forms a continuous line just behind 

 the so-called septomaxillary, while its posterior border is of an irregular 

 waved form. Posteriorly the series is continued behind the eye from the 

 large suborbital by three diminishing bones (fig. 15, 4, 5, 6), the terminal 

 (dorsal) small triangular one of which is attached over the auditory mass 

 close to the tip of the preoperculum and in continuation of the anterior limb 

 of a supratemporal (sup.tem.) triradiate scale bone. Its lower margin forms 

 the upper edge of the branchial aperture, its upper limb overlies the epiotic, 

 while its posterior overlaps the body of the post-temporal. From the latter 

 there passes into this bone, and continued through the dorsal part of the 

 suborbitals, a bony mucus canal. 



Overlapped by part of the suborbitals, and overlapping the hyomandibular, 

 which is completely covered externally by it and the suborbitals, is the 

 preoperculum (fig. 15, pr.oper.), with a curved anterior border, near which 

 it is thickened for a mucus canal. Terminating dorsally in a sharp end, 

 close to the junction of the pterotic and sphenotic, and just external to 

 the hyomandibular articulation, its posterior border forms a longer and 

 sharper curve than its anterior, its ventral edge therefore is nearly hori- 

 zontal, and it terminates anteriorly in a rounded end. 



It largely overlaps the upper edge of the interoperculum (inter. oper.), 

 an elongated bone with its rounded anterior end slightly notched in the 

 middle. The interoperculum overlaps with its lower border the posterior 

 branchiostegal, and with its posterior end the anterior edge of the sub- 

 operculum. 



The latter (sub.oper.) is a somewhat oval-shaped bone, inclining up- 

 wards and backwards. At its upper anterior part is a process, which is 

 * See reference to this in Parker's ''Shoulder Girdle," Phil. Trans. 



