decreasing length posteriorly in the series. At their dorsal 

 ends the pterygiophores are slightly expanded into ar- 

 ticular knobs. The pterygiophores articulate with one 

 another and with the neural spines supporting them by 

 fibrous tissue with little or no interdigitation between the 

 pterygiophores. Just below their expanded articular faces 

 the pterygiophores are slightly constricted so that there 

 is a definite gap between their apposed surfaces. The first 

 pterygiophore is unlike the others only in that it is much 

 larger and more expanded anteriorly and posteriorly in- 

 to a thin plate filling the space between the distal regions 

 of the neural spines of the seventh and eighth abdominal 

 vertebrae. Anterodorsally the first basal pterygiophore 

 articulates by fibrous tissue and interdigitation with the 

 posterior end of the supraneural element or carina. The 

 supraneural is a long strut reaching nearly to the pos- 

 terior end of the skull. Its dorsal surface is laterally ex- 

 panded and its bears a deep ventral keel. Anteriorly the 

 ventral edge of the keel is concave to enclose the distal 

 tips of the neural spines of the third, fourth, and, in one 

 specimen, fifth abdominal vertebrae, articulating with 

 them by fibrous tissue. The distal tips of the neural 

 spines of the sixth and seventh vertebrae end at the ven- 

 tral edge of the keel and do not penetrate it. The dorsal 

 surface of the supraneural lies just below the cuirass. The 

 basal pterygiophores of the dorsal fin articulate between 

 the neural spines of the seventh abdominal to third cau- 

 dal vertebrae. 



Fin rays and pterygiophores. — Eleven fin rays are 

 present; the first ray unbranched, the others branched in 

 up to incomplete triple dichotomies. Distal pterygio- 

 phores are either absent or unossified. The bifid bases of 

 the fin rays articulate by fibrous tissue to nine basal 

 pterygiophores. These pterygiophores are basically 

 similar to those of the dorsal fin except that they tend to 

 be longer, more anteroposteriorly expanded and much 

 more firmly held to one another, usually by extensive in- 

 terdigitation. However, while all of the dorsal fin basal 

 pterygiophores lie in the midvertical plane of the body, 

 only the last four anal fin basal pterygiophores con- 

 sistently lie entirely in this medial plane, the five 

 pterygiophores anterior to them diverging to the right 

 and to the left from their ventral ends, which are in the 

 midvertical plane. The sixth to ninth basal pterygio- 

 phores have their dorsal ends held by fibrous tissue at 

 some distance from the ventral ends of the haemal spines 

 of the first to fourth caudal vertebrae. The second to fifth 

 pterygiophores have their slightly expanded ventral ar- 

 ticular ends in the midvertical plane, but their long more 

 or less rodlike anterodorsally directed portions lie to the 

 right or to the left of the midline in the anterior portion of 

 the large muscle mass connected to the anal fin. In the 

 two study specimens three of these pterygiophores 

 diverge to the right and two to the left. The first basal 

 pterygiophore is expanded just above its knoblike distal 

 end into a thin plate which lies only slightly to one side of 

 the midline. It has the largest keellike expansion of any 



of the pterygiophores. It is the second to the fifth 

 pterygiophores that diverge widely from the midline, two 

 to the left and two to the right. The second to fifth 

 pterygiophores remain rodlike throughout their lengths, 

 while the sixth to ninth pterygiophores, that lie in the 

 midline of the body throughout their lengths, are 

 variously expanded into thin plates for parts of their 

 lengths. The knoblike distal ends of these more posterior 

 basal pterygiophores are closely apposed to one another 

 and articulate by fibrous tissue but they are not fused or 

 sutured. The shafts of the first to fifth pterygiophores are 

 tightly held to one another in the midline before they di- 

 verge to the right or left, and the surfaces of apposition 

 seem to be at least extensively interdigitated, if not, in 

 some cases, perhaps even fused. The concave region on 

 the posteroventral edge of the last basal pterygiophore 

 rests against the edge of the carapace, just as the similar- 

 ly indented region on the last dorsal basal pterygiophore 

 supports the carapace in that region. 



Anatomical diversity. — Very little anatomical 

 diversity is present in this small family of deepwater box 

 fishes comprising about 10 species from the Indo-Pacific 

 (Hawaii to South Africa), but mainly from Australia. 

 They have been relatively poorly collected and the 

 genera as presently recognized (McCulloch and Waite 

 1915; Fraser-Brunner 1935b, 1941c) seem extremely fine- 

 ly split, the distinctions based exclusively on carapace 

 characteristics, many of which are rather trivial (num- 

 ber of spiny processes and degree of development of iso- 

 lated caudal peduncular scale plates). Three of the 

 genera {Kentrocapros,^ Capropygia, Caprichthys) are 

 monotypic, while Aracana and Strophiurichthys each 

 have two species, and Anoplocapros two, perhaps three 

 (if grayi is valid). 



The carapace in all genera except Kentrocapros and 

 Aracana has six major ridges or angles: single dorsal 

 and ventral crests and two paired ridges along the side of 

 the body, dorsolateral and ventrolateral in position. In 

 Kentrocapros and Aracana there is no dorsal crest, the 

 back being relatively flat or gently convex rather than 

 high crested, so that there is a total of five ridges. In the 

 single fossil species of the family, Proaracana dubia 

 (Blainville 1818) from the Eocene of Monte Bolca, Italy, 

 the dorsal crest is well -developed and terminates at its 

 greatest height in a large spiny process similar to that of 

 the ventral crest, spines in these positions being unique 

 in the family. 



In addition to the major ridges, a mediolateral ridge or 

 slightly convex region may be present about midway 

 between the dorsolateral and ventrolateral ridges, but it 

 is usually less distinct than the other ridges. 



The carapace extends further posteriorly and the cau- 

 dal fin is less strongly developed in Caprichthys and 

 Capropygia than in the other genera. 



Posterior to the carapace there are always isolated 



Aracanostracion Smith (1949b) is tentatively considered a synonym 

 of Kentrocapros, until the single known specimen, the type of rosapinto, 

 can be examined. 



