164 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



EXPLANATION OP THE LETTERS OF BEPEEENCE USED IN PLATES 



I-IV. 



ab. Air-bladder. 

 al. Urinary bladder. 

 at. Atrium or venous sinus. 

 ail. Auditory vesicle or internal ear. 

 ba. Bulbus aqrtse. 

 bf. Breast or pectoral fin. 

 6r. Brancliite or branchial arches, 

 cc. Choroid layer of cells ; lamina fusca. 

 ce. Cerebrum. 

 cer. Cerebellum. 



ch. Chorda dorsalis or notochord. 

 chy. Ceratohyal cartilage. 

 cr. Carina. 



C7's. Cardiac sinus; rudiment of pericardiac space. 

 CSC. Caraco-scapular cartilage or rod. 

 cv. Caudal vein. 



ep. Epiblast or sensory skin layer. 

 /. Remains of food in intestine. 

 ff. Fin-fold ; rudiment of breast fin 

 gd. Germinal disk. 

 gp. Germinal layer or pellicle. 



h. Heart. 

 hy. Hyi)oblast or inner mucous layer. 

 hy'. Hyoid cartilage. 

 i, i'. Intestine. 

 Iv. Liver. 



m. Medulla spinalis or spinal cord. 

 mh. Midbrain or optic lobes. 

 mc. Medullary canal. 

 mZ.:. Meckel's cartilage, 

 wo. Medulla oblongata. 

 na. Nasal pit. 



nf. Dorsal and ventral natatory fold or fin. 

 op. Operculum. 

 opv. Optic vesicle. 

 OS. Oil sphere. 

 2)c. Pigment cells. 

 pn. Pineal gland. 

 pp. Papular prominences. 

 q. Quadrate. 

 r. Rim of blastoderm. 



