OCR Text |
Show 1 9 0 4 .] OSTEOLOGY OF CLUPEOID FISHES. 4 5 7 over the hinder half of the ramus ; in Clupea harengus and Clupea sprattus it lies over the front half. The mandibular symphysis is more in advance of the pre maxillae in the two latter species than in the first. The angular bone is distinct. There is a small sesamoid articular in Clupea jinta, but not in Clupea harengus. There are about five teeth situated in a row at the anterior end of the dentary in both species. Hyopalatine Series (text-fig. 124).-As has been pointed out by Matthews (I. c. p. 289), the hyomandibular of Clupea jinta articulates with the cranium by two distinct heads, whereas in Clupea harengus the hyomandibular has a single broad head. On comparing Clupea jinta and Clupea harengus, the quadrate is seen to be more forwardly rotated in the latter, and the hyomandibular to slope more forward. The angle in the middle Text-fig. 124. c Clupea finta, hyopalatine arch, opercular bones, and mandible, left side, mesial aspect. For explanation of lettering see p. 493. of the ectopterygoid, also, is smaller, so that the forward displacement of the quadrate-articular joint does not affect the front part of the hyopalatine arch. It results, however, in the forward extension of the mandibular symphysis in front of the pre-maxillaries, and is accompanied by an elongation of the interopercular and the lower limb of the preopercular. The symplectic is rather small in Clupea jinta; it is relatively longer and more slender in Clupea harengus. The lower end of the symplectic of Clupea jinta is abruptly terminated, and is not enveloped by the quadrate as is so generally the case. The palatine is shorter and broader in Clupea jinta than in Clupea harengus, and has a distinct cartilaginous head for articulation with the prefrontal, whereas in Clupea harengus it is the pre- |