less anteroposteriorly expanded than the latter. The 

 seventh and eighth abdominal vertebrae have their neu- 

 ral spines in the form of long stout shafts between which 

 the first basal pterygiophore of the dorsal fin articulates. 

 Small neural prezygapophyses are present from about 

 the fourth to the last abdominal vertebra, and increase in 

 size posteriorly in the series. From the posterolateral sur- 

 face of the second vertebral centrum a stout ventrally di- 

 rected process is present which makes fibrous tissue con- 

 tact with a similar ventrally directed process from the 

 anterolateral surface of the centrum of the third verte- 

 bra. These ventral processes from either side of these two 

 centra do not meet their opposite members in the mid- 

 line to completely enclose the haemal canal. However, 

 the abdominal vertebrae posterior to the third vertebra 

 have stout ventrally directed processes from the antero- 

 lateral surfaces on either side of their centra which do 

 meet and fuse in the midline to enclose completely the 

 haemal canal. The haemal spines possess posteriorly di- 

 rected flanges along their posterior edges just below the 

 haemal canal. The haemal spines increase in size pos- 

 teriorly in the series and form broad surfaces for muscle 

 attachment. 



Caudal Vertebrae. — In 17 specimens the caudal 

 vertebrae numbered nine. All of the caudal vertebrae 

 possess neural arches and spines and haemal arches and 

 spines. Neural prezygapophyses are present on all of the 

 caudal vertebrae, although they decrease in size pos- 

 teriorly so that the last caudal vertebra has them only 

 weakly developed. The neural spines of the first two cau- 

 dal vertebrae are slender but strong shafts which dis- 

 tally support the more posterior of the dorsal fin basal 

 pterygiophores. These two neural spines are shorter than 

 the last two neural spines of the abdominal vertebrae, 

 which support the more anterior of the dorsal fin basal 

 pterygiophores. The neural spines of the third to sixth 

 caudal vertebrae are slender but strong shafts which are 

 slightly longer than those of the two preceding caudal 

 vertebrae. The neural spine of the seventh caudal verte- 

 bra is enlarged anteroposteriorly, and that of the eighth 

 caudal vertebra is even more enlarged. The neural spines 

 of these two vertebrae make close fibrous tissue contact 

 with one another and form a large thin plate above their 

 centra. Each neural arch possesses a small neural fora- 

 men. The haemal arches and spines of the first three cau- 

 dal vertebrae are like those of the abdominal vertebrae 

 just anterior to them, except that the haemal spine of the 

 first caudal vertebra is even more enlarged posteriorly 

 than are the others and ventrally supports by fibrous 

 tissue the much expanded first basal pterygiophore of the 

 anal fin. The posteriorly expanded platelike portions of 

 the haemal spines of the second and third caudal verte- 

 brae ventrally support through fibrous tissue the second 

 to the fifth (last) anal fin basal pterygiophores. The 

 haemal spine of the fourth caudal vertebra is less antero- 

 posteriorly expanded than are those anterior to it, but it 

 is somewhat longer. The haemal spines of the fifth to 

 seventh caudal vertebrae become increasingly expanded 

 anteroposteriorly so that the haemal spine of the seventh 



is a rounded flat plate whose posterior edge makes 

 fibrous tissue contact with the anterior edge of the much 

 modified haemal spine of the eighth caudal vertebra. 

 Whereas the centrum and the neural arch and spine of 

 the eighth caudal vertebra are fused together, the haemal 

 arch and its spine are autogenous and held to the cen- 

 trum by fibrous tissue and interdigitation. The haemal 

 spine of the eighth caudal vertebra is much enlarged, and 

 possesses a posterior extension which reaches almost to 

 the base of the lowermost caudal fin ray. The edge of the 

 haemal apparatus of the eighth caudal vertebra that 

 makes contact with the centrum is somewhat concave so 

 that a haemal canal is present throughout the length of 

 the region of articulation of the two elements. The hae- 

 mal canal is continuous anteriorly with the haemal canal 

 of the preceding vertebrae, while posteriorly it is continu- 

 ous with the canal between the surfaces of contact of the 

 parhypural and the centrum of the last vertebra. 



Caudal Skeleton. —The caudal complex is composed 

 of four separate bony elements closely held to one 

 another variously by fibrous tissue and interdigitation. 

 The ventral portion of the caudal skeleton is formed by 

 the parhypural, which is broad anteriorly but tapers to a 

 stout shaft posteriorly where it supports the lowermost 

 caudal fin ray. Anteriorly it is extensively interdigitated 

 with the posterodorsal edge of the haemal spine of the 

 penultimate vertebra. A distinct notch is present in its 

 dorsal edge a little forward of its middle region. Anterior 

 to this notch the dorsal edge of the parhypural is exten- 

 sively interdigitated with the region of the centrum of the 

 large bony plate above it, which is the fused centrum- 

 lower hypurals. The notch in the parhypural is the last 

 opening into the haemal canal, the latter being con- 

 nected to the canal in the preceding vertebrae by a longi- 

 tudinal groove medially along the otherwise interdigi- 

 tated articular surface between the parhypural and the 

 centrum anterior to the foramen. The dorsal surface of 

 the parhypural posterior to the foramen is held by fibrous 

 tissue to the ventral edge of the hypural region of the fus- 

 ed centrum-lower hypural plate. The epural is a flat- 

 tened plate closely held by fibrous tissue between the 

 posterior edge of the neural spine of the penultimate 

 vertebra and the anterior edge of the urostylar region of 

 the fused centrum-lower hypural plate and of the antero- 

 ventral region of the upper edge of the autogenous upper 

 hypural plate. Ventrally the epural slightly interdigi- 

 tates with the incomplete neural arch region of the last 

 vertebra, forming the dorsal roof of the neural arch. The 

 neural canal thus enclosed is continuous anteriorly with 

 the canal in the preceding vertebrae, while posteriorly 

 the canal opens to the exterior just behind the end of the 

 area of articulation between the epural and the neural 

 arch of the last vertebra. In large specimens (over 1(X) 

 mm) the articulation between the epural and the lateral 

 walls of the neural arch of the last vertebra tends to be- 

 come more intimately interdigitated and perhaps even 

 fused. Similarly, the articulation of the epural with the 

 neural spine of the penultimate vertebra and the uro- 

 stylar region of the last vertebra tends to become slightly 



