in advance of the base of the dorsal fin. The intemeural 

 process of the first basal pterygiophore lies between the 

 neural spines of the seventh and eighth abdominal verte- 

 brae and those of the last two basal pterygiophores 

 between those of the third and fourth caudal vertebrae. 

 On the upper end of each of the basal pterygiophores 

 there is a short columnar projection whose deeply con- 

 cave surface is cartilage filled, except for the last 

 pterygiophore, which has two of these facets with which 

 the fin rays articulate by fibrous tissue. The pterygio- 

 phores are also cartilage filled at their ventral edges. 

 From its anterodorsal edge the first basal pterygiophore 

 has an anteriorly directed process, lying in the midline of 

 the body just beneath the skin, which reaches to about 

 the level of the tip of the neural spine of the sixth ab- 

 dominal vertebra. At its anterior end it is attached by 

 fibrous tissue to a rodlike supraneural. The supraneural 

 lies just below the skin in the midline of the body from 

 the level of the tip of the neural spine of the sixth ab- 

 dominal vertebra to about the region above the fourth 

 abdominal vertebra. The supraneural is surrounded by a 

 longtitudinal band of muscles which lies between the 

 dorsomedial edges of the general epaxial muscle masses. 

 This longtitudinal band of muscles continues anteriorly 

 and partially fills the space between the bifid neural 

 spines of the first three abdominal vertebrae and ends by 

 connecting firmly with the supraoccipital spine. The 

 ninth, or last, basal pterygiophore has a posteriorly di- 

 rected spine from its posterodorsal edge that ends over 

 the neural spine of the fifth caudal vertebra. The fact 

 that the ninth basal pterygiophore bears two columnar 

 articular facets may indicate that it is a fusion product of 

 two originally separate basal pterygial elements. None of 

 the basal pterygiophores possess lateral projections along 

 its length for muscle attachment. 



the sixth basal pterygiophore, which usually has three of 

 them. From these columnar facets the fin rays articulate 

 by fibrous tissue. The pterygiophores are also cartilage 

 filled at their dorsal ends. As is the case with the last 

 basal pterygiophore of the dorsal fin, the presence of 

 more than one columnar articular process may indicate 

 that the first and the last anal fin basal pterygiophores 

 are the fusion products of two or more originally sep- 

 arate elements. The sixth basal pterygiophore bears from 

 its posteroventral edge a posterior projection that ex- 

 tends back under the haemal spine of the sixth caudal 

 vertebra. None of the pterygiophores possess lateral pro- 

 jections along their lengths for muscle attachment. 



Detailed description of Canthigaster rostrata. 



Material examined. — Five cleared and stained speci- 

 mens, 10.0-59.6 mm, and one dry, partially disarticu- 

 lated skeleton, approximately 96.5 mm. 



SKULL. 



Occipital Region. 



Basioccipital. — A long column, laterally expanded 

 anteriorly; cartilage filled at its anterior and postero- 

 lateral edges; articulates anteriorly by interdigitation 

 with the slightly overlying parasphenoid, anterolaterally 

 with the prootics, and laterally with the exoccipitals. The 

 posterior concave end of the basioccipital is somewhat 

 depressed, its rim articulating by fibrous tissue with the 

 rim of the anterior concave face of the first vertebra. The 

 dorsal edge of the basioccipital forms the ventral wall of 

 the foramen magnum. 



Anal Fin. 



Fin rays and pterygiophores. — Fourteen fin rays 

 present in most specimens, the first two rays and the last 

 one or two rays unbranched, the others branched in 

 single or double dichotomies. The first ray is small and 

 rudimentary, like that of the dorsal fin. Distal pterygio- 

 phores are either absent or unossified. The fin rays are 

 supported below by six basal pterygiophores which are 

 strongly interdigitated with one another ventrally. The 

 "interhaemal" processes of these pterygiophores are 

 large anteriorly in the series but decrease in size pos- 

 teriorly, with the first basal pterygiophore being by far 

 the largest of the series. The first, second, third, and 

 fourth basal pterygiophores articulate by fibrous tissue 

 dorsally with the haemal prezygapophyses of, respec- 

 tively, the first, second, third, and fourth caudal verte- 

 brae. The fifth and sixth basal pterygiophores articulate 

 similarly with about the middle of the haemal arches of, 

 respectively, the fourth and fifth caudal vertebrae. On 

 the ventral surface of each pterygiophore there is a short 

 columnar projection whose ventral edge is deeply con- 

 cave and cartilage filled, except for the first basal 

 pterygiophore, which has two of these projections, and 



Exoccipital. — Cartilage filled at its anterior and 

 ventromedial edges; articulates by interdigitation ven- 

 tromedially with the basioccipital, ventrolaterally with 

 the pterotic, anterodorsally with the epiotic, and dorso- 

 medially with the supraoccipital. At the extreme pos- 

 terior end of its dorsomedial edge the exoccipital inter- 

 digitates with its opposite member to form the dorsal 

 wall of the foramen magnum, while the posteromedial 

 edges of the exoccipitals form the lateral walls of that 

 foramen. From its posteroventral edge the exoccipital 

 condyle projects posteriorly well past the posterior end of 

 the basioccipital and articulates by fibrous tissue over 

 the lateral surface of the anterior half of the centrum of 

 the first vertebra. 



Supraoccipital. — Flattened anteriorly, but drawn 

 out into a deep laterally compressed spine posteriorly; 

 cartilage filled along its anterior edge; articulates by in- 

 terdigitation anteriorly with the frontals, which 

 somewhat overlie it, laterally with the epiotics and pos- 

 terolaterally with the exoccipitals. The posterior edge of 

 the supraoccipital spine is slightly expanded laterally, 

 particularly in the dorsal region. The spine does not pro- 

 ject posteriorly far beyond the end of the skull. 



