of the Fishery Board for Scotland. 



293 



Plate XVIII. 



Fig. 22. Upper aspect of skull, with frontal, &c, membrane bones removed. 

 Fig. 23. Posterior view of skull. 



Fig. 24. Transverse section (looking back) through posterior end of cranium 

 (through posterior air vesicle). 



Fig. 25. Transverse section (looking back) through orbit, showing anterior 

 end of cranium in elevation). 



Fig. 26. Outer aspect of left pectoral girdle. 



Fig. 27. Inner aspect of left pectoral girdle. 



Fig. 28. Outline (camera lucida) side view of tail of 38 mm. herring, the 

 caudal fin rays being omitted ( x about 32). 



Note. — All the figures, unless otherwise stated, are twice natural size. 



Reference Letters. 



a.c. articular cup for neural arch. 

 al. alisphenoid. 



a.h.mn. anterior part of hyomandi- 



bular. 

 am. ampulla. 

 an. angular. 



ar.h. articular cavity of hyomandi- 



bular. 

 art. articular. 



a. s.ves. anterior spherical air vesicle. 

 au.f. auditory fenestra. 



b. ar. branchial arches. 

 b.br. basibranchial. 



b.im. branched intermuscular bone. 

 b.oc. basioccipital. 

 b.p % basal piece of haemal arches. 

 br.o. brachial ossicles (of pectoral 



girdle). 

 br.r. branchiostegal rays. 



b. sph. basisphenoid. 



cav. postero - lateral concavity of 

 skull. 



cav. sac. cavity containing sacculus of 

 ear. 



c. br. cerato-branchial. 

 cl. clavicle. 



cl.h. clavicular hook. 

 cl.pr. clavicular process. 

 cor. cornu. 

 cr. coracoid. 

 den. dentary. 



e.br. epibranchial (4th upper pharyn- 

 geal). 

 ec.eth. ectethmoid. 



e. m.c. eye muscle (recti) canal. 

 ep. epiotic. 



ep.hy. epihyal. 

 eth. ethmoid. 



eth.r. mesethmoidal ridge. 



eth.pal. ethmo-palatine cartilaginous 



boss. 

 ex.oc. exoccipital. 



/. skin-covered interval between 

 premaxilla and maxilla. 



f. m. foramen magnum. 



for. lateral foramen of skull. 

 fr. frontal bone. 



fr.p. lateral process of frontal bone. 



ho3m. haBmapophysis. 



h.br. hypobranchial. 



hd. head of rib. 



hm.n. hyomandibular. 



h.s.c.c. horizontal semicircular canal. 



h. z. anterior ventral (hsemal) zyga- 

 pophysis. 



im. intermuscular bone. 



i. hy. interhyal. 

 in.oper. interoperculum. 



jugal. 

 I. labials. 



lam, posterior lamina on rib. 



m.cav. median cavity in cartilage 



containing oblique eye muscles. 

 mn. mandible. 

 mt.pt. metapterygoid . 

 mx. maxilla. 

 na. nasal bone. 

 n.ap. neural appendage. 

 n.cap. nasal capsule. 

 n.sp. neural spine. 

 oper. operculum. 

 op.ot. opisthotic. 

 o.sph. orbito-sphenoid. 

 pal. palatine. 

 par. parietal. 



p. br. ph ary ngo -bran ch i al s. 

 p.cr. post coracoid. 



p.cl. 1, 2, 3. the three segments of 



post clavicle. 

 pha.5. lower pharyngeal bone (5th 



cerato-branchial). 

 pl.pt.car. palato-pterygoid cartilage. 

 p.ot. prootic. 



pr. posterior process of vertebra 

 (young). 



pr.mx. premaxilla. 



pr.oper. preoperculum. 



p.s.s.c. posterior vertical semi- 

 circular canal. 



p.sph.w. posterior wings of para- 

 sphenoid. 



ps.ves. posterior spherical air vesicle. 



p.tem. post-temporal. 



pt.f. part of prootic on which rests 



the pituitary body. 

 pt. pterygoid. 



