A treatise on zoology . The l)asidorsals and interdorsals vary greatly inrelative development; they frequently surround the roof of the neural canal may l)e closed above (as in Elasmo-branchs) by a row of median or paired elements, the the top of these runs the longitudinal ligament. Above thi» TAIL loi ligament generally occur a row of spinal elements. These medianspines form the connecting link between the axial skeleton of thevertebral column (see pp. 69 and 105) and the appendicular skeletonof the median tins ; possibly (Goette [167]) they should be reckoned
A treatise on zoology . The l)asidorsals and interdorsals vary greatly inrelative development; they frequently surround the roof of the neural canal may l)e closed above (as in Elasmo-branchs) by a row of median or paired elements, the the top of these runs the longitudinal ligament. Above thi» TAIL loi ligament generally occur a row of spinal elements. These medianspines form the connecting link between the axial skeleton of thevertebral column (see pp. 69 and 105) and the appendicular skeletonof the median tins ; possibly (Goette [167]) they should be reckonedrather with the latter than with the former. Assuming that the different types of vertebral arches found infish have been evolved from such a primitive complex structure, wefind that in the course of specialisation the basidorsals and Ijasi-ventrals persist genei-ally as the most important elements, while theothers tend to disappear, or to fuse with them. Both the dorsal libs and the pleural ribs may be considered as. Dissected tail of PohipUrKS birhir, GeortV. (After KiUliker.) , anal fin ; , epichordal fin ;fit doi-sal tiulet; , liaeiiial aroh ; , liypocliordal tin ; , neural spnie ; , slightly up-turned tip of the notocliord ; r, endoskeletal radial; sc, scales. The proximal ends of thedermal rays have been cut off to expose tlie radials and tip of the notochord. This tail proi>aljly secondarily diphycercal. prolongations of the basiventrals ; these basals may remain separateor autogenous when ossified (in many primitive Teleostei (, 358), tail of Amia, etc.), or they may fuse with the the ribs or the l)asiventrals may undergo reduction anddisappear. In the formation of the haemal canal behind the abdominalregion it is the basiventral, not the pleural ril) which becomes thehaemal arch. The haemal spine is sometimes separate (Amia), butoften appears to be merely a prolongation of the arch (mostTeleosts, Fig. 63), and tlie ribs
Size: 2065px × 1210px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublishe, booksubjectzoology
