. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Figure 7. Epiotic-Supraoccipital Relationship (posterior view): A. Maurolicus muelleri; B. Polyipnus asteroides; C. S/ernoptyx pseuc/ofascuro; D. Argyropelecus bemigymnus. Abbreviations: EPO =^ epiotic; SOC = supraoccipital. which contains pecuHarly shaped and very large otoHths (Kotthaus, 1967). Abdominal keel scales (Figs. 8-11). Polyipnus and Argijropelecus have de- veloped ossified plates (modified scales) which form a keel and serve to give struc- ture to the abdominal region and associ- ated photophore groups. S
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Figure 7. Epiotic-Supraoccipital Relationship (posterior view): A. Maurolicus muelleri; B. Polyipnus asteroides; C. S/ernoptyx pseuc/ofascuro; D. Argyropelecus bemigymnus. Abbreviations: EPO =^ epiotic; SOC = supraoccipital. which contains pecuHarly shaped and very large otoHths (Kotthaus, 1967). Abdominal keel scales (Figs. 8-11). Polyipnus and Argijropelecus have de- veloped ossified plates (modified scales) which form a keel and serve to give struc- ture to the abdominal region and associ- ated photophore groups. Several plates appear posterior to the pelvic fins; most are anterior to them. The plate size, niun- ber, and distance between plates is less well developed in Polyipnus. Stemoptyx seems also to have a keel-like structure, but this is not ossified. The gonostomatids examined have little keel development and no ossification in this region. Anal pterygiophores (Figs. 8-11). In stemoptychids, the anal pterygiophores show a characteristic gap. Several pterygio- phores are associated with and between the same haemal spine forming a circular gap. In this respect the P. spinosiis species complex is the least well developed. In the gonostomatids examined there is one pterygiophore for each haemal spine with no gap. The anteriormost anal pterygio- phore possesses flangelike processes pro- jecting laterally in Polyipnus, Stemoptyx, and Maurolicus. The former two have, in addition, pronounced ventral processes lacking in Maurolicus. Argyropelecus has no processes, although the anal pterygio- phores are enlarged. Photophores. The glandular nature and pattern of photophores seem to indicate some relationship among all genera studied. The trend appears to be from a condition of an essentially unbroken row of photo- phores on the ventral body surface (Maurolicus) to one in which this row is broken both horizontally and vertically (stemoptychids). As before, Polyipnus is intermediate in this re
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