FISHERY BULLETIN: VOL 71, NO. 3 



Table 7. — Size in millimeters at which certain bones 

 begin to ossify in Eiropus inicrostomus and Citharich- 

 thys arctifrons. 



Citharichthys arctifrons 

 12.3 mm 



Figure 9. — Composite illustration of bones of the bran- 

 chiocranium and of the pectoral and pelvic girdles 

 (shaded) of young Eiropus microstomits and Citharichthys 

 arctifrons. The ossified part of the neurocranium in- 

 cluding the parasphenoid is outlined. Upper and lower 

 jaws: A - premaxillary, B - maxillary, C - dentary, D - 

 articular and angular process. Oromandibular region: 

 E - ectopterygoid, F - quadrate, G - endopterygoid, 

 H - hyomandibular, J - symplectic. Opercular series: 

 L - preopercle, M - opercle, N - interopercle, O - sub- 

 opercle. Hypobranchial region: P - branchiostegal rays, 

 Q - urohyal, R - interhyal, S - hypohyal, T - ceratohyal, 

 U - epihyal. Pectoral and pelvic girdles: V - cleithrum, 

 W - supracleithrum, X - posttemporal, Y - postcleithrum, Z 



Item 



Bone'^ Eiropus Citharichthys 



type microstoinus arctifrons 



Upper and lower jaws: 



A Premaxillary D ?- 4.9 



B Maxillary D ?- 4.9 



C Dentary D ?- 4.9 



D Articular C ?- 4.9 



Angular process D 8.0- 8.9 



Oromandibular region: 



E Ectopterygoid D 4.0- 5.9 



F Quadrate C 5.0- 5.9 



G Endopterygoid D 5.0- 6.9 



H Hyomandibular C 5.0- 6.9 



J Symplectic C 7.0- 7.9 



K Palatine C 9.0- 9.9 



K' Metopterygoid C A AA3 



Opercular series; 



L Preopercle D 



A/\ Opercle D 



N Interopercle D 



O Subopercle D 



Hypobranchial region: 



P Branchiostegal rays D 4.0- 5.9 



Q Urohyal D 6.0- 6.9 



R Interhyal C 7.0- 7.9 



S Hypohyals C 7.0- 7.9 



T Ceratohyal C 7.0- 7.9 



U Epihyal C 7.0- 7.9 



U' Basihyol C AM 



Pectoral and pelvic girdles: 



V Cleithrum D ?- 4 

 W Supracleithrum D 4.0- 5 

 X Posttemporal D 5.0- 6 



Y Postcleithrum D 5.0- 6 

 Z Basipterygium C H.0-12 

 Z' Scapula C AM 

 Z" Coracoid C AM 

 Z'" Radials C AM 



?- 4.9 



?- 4.9 



5.0- 6.9 



5.0- 6.9 



' The smallest stained larvae examined were 4 mm. 

 ■^ D - Dermal bone. 



C - Cartilage replacement bone. 

 ^ A M - After metamorphosis. 



ment of the adult complement of pelvic fin rays 

 (Table 6) and possibly completion of metamor- 

 phosis — about 12 mm in E. microstomus and 

 sometime before 16 mm in C. arctifrons. Time 

 and sequence of ossification of the scapula, 

 coracoid, and radials are unknown. They are 

 ossified in juveniles of 40 mm. Ossification 

 probably corresponds with pectoral fin forma- 

 tion. 



Structurally, bones in these girdles are similar 

 in both species. The posterior extension of the 

 basipterygium on both sides is longer in juvenile 

 and adult E. microstomus (Figures 10,11). The 

 posttemporal of the eyed and blind side is 

 relatively smaller in adult C. arctifrons. 



basipterygium. 



754 



