THE OSTEOLOGY OP AMIURUS OATUS. 447 



PLATE II. 



Fig 1. — Surface view of skull of Amiurus cat us. A «=adnasal, Eeth =ecteth- 

 moid, EpO=e])iotic, Fr = frontal, Hmd - hyornaudibular, I0p= 

 interoperculum, MEtk — mesethmoid, ilf7i=mandible, JfP£=meta- 

 pterygoid, ilfcc=maxilla, ZVa=nasal, Op = operculum, Pa = pala- 

 tine, Pmx — premaxilla, P?-0/?=preoperculum, P£0=pterotic, Qu= 

 quadrate, 5W=supraclavicle, #0=supraoccipital, & r /;j0=sphenotic, 

 iZ=membrane bone in fascia of add. arc. pal. 



Fig. 2. — Cranium of Amiurus catus seen from the side and slightly from be- 

 low. In addition to certain letters used in Fig. 1, there are the 

 following : — <4s=alisphenoid, PO=basioccipital, ExO = exoccipi- 

 tal, Pa§=parasphenoid, Pr/=ectethmoid, PrO - prootic, VO= 

 vomer, VIII. =foramen for glossopharyngeal, IX.=foramen for 

 vagus. 



Fig. 3. — Lower half of left branchial arches of Amiurus nigricans. Cbr 1 , 5 ^= 

 ceratobranchials 1-5, Gp t 4 =copuhe 1-4, iP'r 1 _ 4 =hypobranchials 

 l^t, P/(,/=pharyngeum inferius. 



Fig. 4. — Upper half of right branchial arches of Amiurus nigricans from 

 above. l£&r 14 =epibranchials 1-4, P6r 2 ^ 3 =pharyngobranchials 2 

 and 3, j pro=process of epibranchial 3, PA<S'=pharyngeum superius. 



Fig. 5. — Posterior vertebra; and arches of A. nigricans. _$" 1 ^ 6 =neural arches 

 and spines, i7 T6 =rhfemal arches and spines, A and P=two lower 

 haemal arches without centra, C. D, E and P=four upper hasmal 

 arches without centra, iVS=osseous sheath of notochordal filament. 



Fig. 6. — Pectoral arch of A. catus. .M"C7=mesoclavicular portion ; Id— infra- 

 clavicular portion ; Cor=coracoid ; &c=scapular portion ; ap, mp, 

 ip=anterior, median and inferior process of mesoclavicle ; wp=rrod- 

 like process of coracoid ; /or=foramen between coracoid and sca- 

 pula ; .s-r7=semicircular groove on mesoclavicle for first ray ; r= 

 ridge in coracoid ; 6r=bridge-like process on coracoid which arti- 

 culates with infraclavicle ; .sp=bridge-like spiculum. 



Fig. 7. — Anterior ray of pectoral fin of A. catus. »SV=semicircular ridge, ; tps 

 and <p£— superior and inferior terminal processes. 



Fig. 8. — Transverse section through the pterotic region of a very young A. 

 catus. P<9£=pterotic cartilage ; Int= integument ; He ^horizontal 

 semicircular canal ; HM = hyomandibular cartilage ; MG= mucous 

 canal with a ring of bone around it. 



Fig. 9, — Longitudinal section through the anterior portion of the mandible of 

 a very young A. catus. Mck= Meckel's cartilage ; 7'=teeth ; cp= 

 cement plates ; Pc=perichondral bone ; i/(7=mucous canal with 

 ensheathing bone. 



Fig. 10. — Transverse section througn a very young A. catus, immediately in 

 front of the dorsal fin. The lateral musculature has been omitted. 

 hit — integment ; %>— an t er io r portion of horizontal plates of dorsal 

 fin (1st ray) ; Isp 1 3 — interspinalia 1, 2 and 3 ; Spp±— spinous 

 process of fourth vertebra ; 7 7 j p 1 =expanded transverse process of 

 fourth vertebra ; ^V^4.5=neuralarch of fifth vertebra; NC=noto- 

 chord ; N— nervous cord ; Ao — aorta ; ilfsc=muscle. 



