of its anterior edge which articulates by fibrous tissue 

 with the third epibranchial; the dorsal end of the fourth 

 epibranchial articulates with the third pharyngobranchial. 



Fifth arch. — Ceratobranchial (lower pharyngeal) 

 element only. Fifth ceratobranchial a stout shaft with a 

 small medial expansion in about the middle third of its 

 length; articulates ventrally with the base of the fourth 

 ceratobranchial; toothless. 



PAIRED FIN GIRDLES. 



Pectoral Fin. 



Supracleithruin. —In position at about a 45° angle 

 to the axis of the body; a stout shaft with a lateral flange 

 along most of its length; articulates by fibrous tissue 

 anterodorsally with the slight concavity on the lateral ex- 

 pansion of the pterotic and ventrally with the cleithrum, 

 which it broadly overlies. 



Cleithrum. — Laterally expanded along most of its 

 length; articulates by fibrous tissue dorsally with the 

 overlying supracleithrum and with the anterior end of 

 the dorsal postcleithrum, which it overlies; along its pos- 

 terior edge it articulates by fibrous tissue with the scapu- 

 la and coracoid. Ventromedially the cleithrum articu- 

 lates by fibrous tissue with its opposite member in the 

 midline of the body between the medial edges of the 

 platelike portions of the first branchiostegal rays. 



Postcleithra. —The postcleithra form a stout strut 

 along the abdominal wall musculature from the 

 supracleithrum to halfway back the length of the ab- 

 dominal cavity. The dorsal postcleithrum articulates by 

 fibrous tissue anterolaterally with the overlying 

 cleithrum and posteroventrally with the ventral post- 

 cleithrum, which tapers to a point posteriorly. The dorsal 

 and ventral postcleithra are only slightly laterally com- 

 pressed. 



Coracoid. —Rounded dorsally but gradually 

 tapering to a stout shaft ventrally; along the dorsal third 

 of its length the posterior edge of the coracoid is in- 

 turned to form a medial flange whose dorsal edge is pro- 

 longed into a spinelike process below the fourth actinost; 

 cartilage filled at the edge of its rounded dorsal portion 

 and at its extreme ventral edge; articulates by fibrous 

 tissue anteriorly with the cleithrum and through car- 

 tilage dorsally with the scapula and last two actinosts. 



Scapula. — Scapular foramen not entirely enclosed 

 by the scapula, but, rather, with its anterior edge closed 

 by the cleithrum; cartilage filled at its anterior and ven- 

 tral edges; articulates anteriorly by fibrous tissue with 

 the cleithrum, ventrally through cartilage with the cora- 

 coid, posterodorsally by slight interdigitation with the 

 anterior edge of the first actinost, and posteroventrally 

 by slight interdigitation with the ventral edge of the sec- 

 ond actinost. 



Actinosts. —Four elements; all cartilage filled at 

 both ends, except for the first actinost, which is filled 

 with cartilage only at its dorsal edge. First actinost 

 reduced to a triangular wedge between the upper parts of 

 the scapula and second actinost, to both of which ele- 

 ments it interdigitates. Second actinost rounded dorsal- 

 ly, constricted in the middle and reduced ventrally to a 

 narrow splint that interdigitates ventrally with the 

 scapula and posteriorly with the base of the third acti- 

 nost; articulates by interdigitation anterodorsally with 

 the first actinost and posterodorsally with the third acti- 

 nost. Third and fourth actinosts slightly constricted in 

 the middle; the third actinost articulating dorsally and 

 ventrally by interdigitation with the second and third 

 actinosts, while it articulates through cartilage just be- 

 low its base with the coracoid; the fourth actinost ar- 

 ticulating by interdigitation anterodorsally and antero- 

 ventrally with the third actinost and ventrally through 

 cartilage with the coracoid. Distally the actinosts sup- 

 port all of the fin rays. 



Fin rays. —Usually 17 fin rays present; the first fin 

 ray short, about one-third or one-fourth the length of the 

 second ray, but normal in shape and symmetry, its two 

 halves of equal size; all rays articulated by fibrous tissue 

 with the dorsal ends of the actinosts. The first tv/o or 

 three rays unbranched, the other rays branched. The first 

 ray without cross-striations, the others cross-striated. 



VERTEBRAL COLUMN. —All vertebrae with bicon- 

 cave centra, except the last, which ends posteriorly in the 

 urostylar process and fusion with some of the hypurals. 



Abdominal Vertebrae. 



First vertebra. — Neural spine bifid and relatively 

 short; neural arch with a complete bony roof over the 

 neural canal, as do all the other vertebrae; articulates by 

 fibrous tissue over the anterior half of the lateral surface 

 of its centrum with the posteriorly projecting exoccipital 

 condyles, while the rim of the concave anterior face of its 

 centrum articulates with the rim of the concave pos- 

 terior end of the basioccipital. Posteroventrally on its 

 lateral surface the centrum of the first vertebra pos- 

 sesses a flattened posterior process which fits under the 

 anterior half of the ventrolateral surface of the centrum 

 of the second vertebra. 



Other abdominal vertebrae. — In 17 specimens the 

 abdominal vertebrae numbered eight. The second and 

 third abdominal vertebrae have their neural spines bi- 

 fid, but somewhat longer than that of the first vertebra. 

 The fourth vertebra has its neural spine enlarged antero- 

 posteriorly, and while it is bifid anteriorly, it becomes 

 single posteriorly. All of the vertebrae, both abdominal 

 and caudal, posterior to the fourth abdominal vertebra 

 have undivided neural spines. The neural spines of the 

 fifth and sixth abdominal vertebrae are of about the 

 same height as that of the fourth vertebra, but they are 



