664 



SCANDI.VAVIAN FISHK: 



oiitsidi^ th(t li-\-oiiKiii(libul:u- lioiicj ;iiul is iiiiited above 

 to tin- interior iiiiirgin of" the siil)()rliit;ii hones. The 

 obliquely ascending branch of the si/mplecticum, on the 

 other hand, is separated by a space, occvi])ied by the 

 masticatory muscles, from the two posterior suborbital 

 bones, \vliicii bound tiie orbit below, liut is united to 

 tlie hind su]ieri((r curner of the aiilcrinr sub(.irl)ital (tlie 

 pi'eorbitaj) bone, where the hitter meets the lateral 

 etlnuoid iione. The foremost suborbital bone forms the 

 greater [)art of the side of the snout, l)eing united in 

 front us a covering bone to the eiito-(meso-)ptery- 

 goidcum and tlie (piadrate bnuc, but leaving behind the 

 latter an o|)(_-niug in tliu middle for about a third of 

 the depth of the snout: the middle suborbital bone is 

 united bekiw to the symplecticum : tiie hindmost sub- 

 orliital bone both to the sympJectlcum and, behind, to 

 the iireoperculum. We refer to the opercidar apparatus 

 a nafrow, lancet-sha].ted, thin bone which lies along tlie 

 inside <jf the horizontal, forward branches of the jire- 

 opei'culum and the ^iynqilcrticuni and the horizontal, 

 backward liranch of the f|uadrate bone. This lancet- 

 shaped bone is united by ligaments Ijehind to the up]ier 

 part of the ceratolivoid bone and in front to tlic an- 

 gular part of the lower jaw. The latter union clearly 

 shows that the bone must be an interoperculum", cor- 

 responding most nearly in form and position to the 

 intero|)erculuni in Trfrodoii for example, though here 

 it has jiassed within the sjinipJecticiim and become united 

 behind to the upper part of the outside of the ceratd- 

 liyoideum, instead of retaining its union to the sub- 

 operculum'', which is here reduced to an extremely 

 thin disk within the lower margin of the operculum. 

 The hnvcr jaw is remai-kalilc for its extraordinary 

 de})tli behind and its sharply curved and toothless dental 

 part. The maxillary bones are comjiaratively well- 

 developed and their hind (lower) extremity is expanded; 

 but the toothless intermaxillaries are small, styliform, 

 and without nasal processes. Tiie palatine bones are 

 shorter than the niaxillaries and of fnrly uniform 

 breadth. At the anterior angle of the union of each 

 palatine bone to the toj) of the ascending branch of the 



quadrate bone we tind the narrow pter\'goid bone, which 

 is Ijent at an obtuse angle, and behind the said union, 

 el(;se t(i the I'idge of the snout, the entoptcrygoid bone, 

 which is luiited in the same manner to the quadrate 

 bone. 



The tongue is wanting, and the glossohyoid bone 

 can liai'illy be discerni'd: Ijut the urohyoid bone is cora- 

 jjaratively long. When the last bone is drawn back, 

 the anterior (lower) end of the ceratolivoid bone with 

 the tip iif the whole branchial apjiaratus is foived down- 

 wards', the ca\itv of tlie mouth iieing thus widened 

 and filled with a fresh sup|il\- nf water. In this manner 

 the Lt)phobranclis puuqi in their food together with the 

 water needed for tJK'ii' respiration. The method in 

 which the transverse derinaHblds (ci^a) just behind the 

 jaws assist to this end, has already been touched upon. 

 The gill-rakers are small, denticulate, and peetinately 

 arranged along liotli mai'gins nf the inside of the liranchial 

 arches. Their function, the prevention of food and fo- 

 reign substances from penetrating into the gill-cavities 

 when the fish swallows, has ali-eady been pointed out 

 by Retzius''. 



The intestinal canal (tig. 170) is simple in all the 

 Lophobranchs, but shortest in the Stjtignatli'uKr. In the 

 Hippocampina; (the Sea-horses) the intestine forms at 

 least a few curves, but in the Si/nijiiathiii(e it is straight 

 or neai'ly so, thus rendering the wliole digestive canal, 

 from the [iharynx to the vent, e(pial in length to or 

 only slightly longer than the abdominal cavity. The 

 lines of demarcation between the oesophagus, the sto- 

 mach, and the intestine are only internal, and consist 

 merely in the difference of the mucous membrane, 

 while the lieginning of the last division is marked as 

 usual liy the mouth of the gall-duct. Puit the small 

 intestine is divided from the rectum by an annular 

 valve. No pyloric aii])endages can be traced. The me- 

 senterium is wanting or only partly developed, in front 

 and behind, to bind the stomach and intestine to the 

 dorsal wall of tlie abdominal cavity. Both the ovaries 

 and the testes are paired, simple, and elongated. Their 



" .J. Playfaik McMuRRicii {lln the Osteoloi/i/ mnl DeceUipmeid of ,Si/ihjii:itiitis Pni-iriiiKS — Qiuirt. .loiirii. Jlirr. Sc. n. scr., No. Xl^II 

 (Oct. 1883), p. 623), nssiimes tlial tliis bone is a nielapterygoid. 



'' See, however, below, on tlie ligamentous connexion.s between us i-p/'lii/nlf. tlie intcropercnlnni, ami tlic .-ingulnr part of llu' lower jaw 

 in ,SV/„;7/.5. 



'■ See for example our lisun- of Si/,i,ju<itliiis acm-. The entire ligiire (.1) shows the eeralohyoiil bones depressed to a pointed pro- 

 tnbcrance on the throat jnst behind the perpendicular from the eye; and in the lower figure (tlie anterior part of the ventral side of the 

 body, /)) the nrohj'oid bone extends back from the ceratohyoid bones find between the opcrcula. 



■^ Atiatomisk uiidentilcning iifcer na<jva ddiir af Sijngimthus Acus och Ophidion, Vet. Akad. Ilandl. 1833, p. 146. 



