THE OSTEOLOGY OF AMIURUS CATUS. 447 
PLATE II. 
Fie 1.—Surface view of skull of Amiuwrus catus. An=adnasal, Heth—=ecteth- 
Fia. 
Fria. 
Fie. 
Fie. 
Fie. 
Fie. 
Fig. 
Fic. 
moid, Hp0=epiotic, #r = frontal, Hmd = hyomaudibular, JOp= 
interoperculum, Mth = mesethmoid, Mnm—mandible, MPi=meta- 
pterygoid, Mz=maxilla, Na=nasal, Op = operculum, Pa = pala- 
tine, Pmx—premaxilla, PrOp=preoperculum, PtO=pterotic, Qu= 
quadrate, Scl=supraclavicle, SO=supraoccipital, SpO—sphenotic, 
H=membrane bone in fascia of add. are. pal. 
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 :—4As=alisphenoid, BO—basioccipital, HeO = exoccipi- 
tal, PaS=parasphenoid, Prf=ectethmoid, PrO = prodtic, VO= 
vomer, V///.=forameu for glossopharyngeal, IX.=foramen for 
vagus. d 
3.—Lower half of left branchial arches of Amiurus nigricans. Chr,.;= 
ceratobranchials 1-5, Cp,_,—=copulie 1-4, Hbr,_,=hypobranchials 
1-4, PhJ=pharyngeum inferius. 
4.—Upper half of right branchial arches of Amiurus nigricans from 
above. Hbr,_,=epibranchials 1-4, Pbr, -,—pharyngobranchials 2 
and 3, pro=process of epibranchial 3, PhS—pharyngeum superius. 
5.—Posterior vertebre and arches of A. nigricans. N,.,—=neural arches 
and spines, H; ,=hzemal arches and spines, A and B=two lower 
hemal arches without centra, C. D, H and F=four upper hemal 
arches without centra, .S—osseous sheath of notochordal filament, 
6.—Pectoral arch of A. catus. MCl=mesoclavicular portion ; /cl=infra- 
clavicular portion; Cor=coracoid ; Sc=scapular portion ; ap, mp, 
ip=anterior, median and inferior process of mesoclavicle ; wp—rod- 
like process of coracoid ; for=foramen between coracoid and sca- 
pula ; sg=semicircular groove on mesoclavicle for first ray ; r= 
ridge in coracoid ; br=bridge-like process on coracoid which arti- 
culates with infraclavicle ; sp—bridge-like spiculum. 
7.—Anterior ray of pectoral fin of A.catus. Sr=semicircular ridge, ; tps 
and ¢pi=superior and inferior terminal processes. 
. §.—Transverse section through the pterotic region of a very young A. 
catus. POt=pterotic cartilage ; Jnt=integument ; Hc=horizontal 
semicircular canal ; HM = hyomandibular cartilage ; M@C—mucous 
canal with a ring of bone around it. 
9,—Longitudinal section through the anterior portion of the mandible of 
avery young A. catus. Mck=Meckel’s cartilage ; T=teeth ; cp= 
cement plates ; Pe=perichondral bone ; MC=mucous canal with 
ensheathing bone. 
10.—Transverse section througn avery young A. catus, immediately in 
front of the dorsal fin. The lateral musculature has been omitted. 
Int =integment ; hp=anterior portion of horizontal plates of dorsal 
fin (Ist ray); /sp,_,=-interspinalia 1, 2 and 3; Spp,--spinous 
process of fourth vertebra ; 7p,—expanded transverse process of 
fourth vertebra ; .VA5=neural arch of fifth vertebra ; NC=noto- 
chord ; NV=nervous cord ; Ao=aorta; Msc=muscle. 
