A treatise on zoology . aws, the position of the lateral line, and the presence of«eratotrichia. They resemble the Cladoselachii in general shape,in the jaws, fins, and heterocercal tail, and in the circumorbital ringof plates. It would be interesting to compare the finer structureof the scales in these two groups. Dean [103] considers the Acan-thodii to be related to, but more specialised than, the Cladoselachii. 192 ACANTHODII Family Diplacaxthidae. The spines are miicli developed, may beserrated and grooved ; they usually occur between the pectoral andpelvic fins. In Dij^lacantJiiis there a
A treatise on zoology . aws, the position of the lateral line, and the presence of«eratotrichia. They resemble the Cladoselachii in general shape,in the jaws, fins, and heterocercal tail, and in the circumorbital ringof plates. It would be interesting to compare the finer structureof the scales in these two groups. Dean [103] considers the Acan-thodii to be related to, but more specialised than, the Cladoselachii. 192 ACANTHODII Family Diplacaxthidae. The spines are miicli developed, may beserrated and grooved ; they usually occur between the pectoral andpelvic fins. In Dij^lacantJiiis there are two pectoral spines on eacli side(Fig. 163). There are two dorsal fins, and usually clavicular plates. Diplacanthus, Ag. (Fig. 156, A); Parexus, Ag. : Mesacanthus (, B); IscJr/iacanthus, Eg.; Devonian, Scotland. Climatius, Ag.(Fig. 164, A); Devonian, Scotland and England. Family Acanthodidae. The intermediate spines are vestigial orabsent; the remaining spines are more slender ; there is only a single dy^s. d. Fig. VA. A Climatius scutiger. Eg., Lower Old Ked Sandstone, Forfarshire ; B, Mesacanthus Mitchell!,E ibid -C , Ag.,howeTCaTbomfeTOUs,EdmhnTgh; J), ,Roemer Lower Permian, Bohemia; restored outlines. (A after A. S. Woodward, B and Cafter Traquair, D after Fritsch, from A. S. Woodward, Proc. Geol. Assoc.) a, anal, rf, dorsal,J), pectoi-al, and v, pelvic fins ; , paired ventral spines. dorsal fin ; and the pelvic fin tends to dwindle in size as the pectoralbecomes larger. Acanthodes (AcantJioessus), Ag. ; Devonian, Europe and X. America(Fi. 164, C and D); Carboniferous and Permian, Europe. ^ (Fig. 158); Devonian, Scotland. Acanthodopsis, R. and A.; Car-boniferous, Great Britain. Protacanthodes, Ft. ; Permian, Europe. Incertae sedis. Family Gyracaxthidae. Isolated large spines and small tubercles^ found in Palaeozoic deposits, and to which the names Gyracanthus and Oracanthus have been given, have long been
Size: 1862px × 1342px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublishe, booksubjectzoology
