. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Fig. 7. Trunk musculature: anterior part, lateral view. A, C/i/omydose/ochus anguinens; B, Chimaera monstrosa. a,b,c,d. Divisions of hypaxial musculature; /., lateral line; ^, inferior oblique; , superior oblique; , rectus profundus; line xy, dorsal limit of inferior oblique. (After Maurer.] sheet inserts, as one would expect, upon the pectoral girdle. Maurer (1912), who di- vides the hypaxial muscles into superior oblique, median oblique, and inferior oblique groups, regards the holocephalian sheet as bei
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Fig. 7. Trunk musculature: anterior part, lateral view. A, C/i/omydose/ochus anguinens; B, Chimaera monstrosa. a,b,c,d. Divisions of hypaxial musculature; /., lateral line; ^, inferior oblique; , superior oblique; , rectus profundus; line xy, dorsal limit of inferior oblique. (After Maurer.] sheet inserts, as one would expect, upon the pectoral girdle. Maurer (1912), who di- vides the hypaxial muscles into superior oblique, median oblique, and inferior oblique groups, regards the holocephalian sheet as being a modification of the in- ferior oblique portion. For Maurer, the state of the inferior oblique in the Holo- cephali represents a more highly evolved condition than exists in any other carti- laginous fish. In the arrangement which Maurer believes is primitive—that seen in Chlamydoselaclie and Heptanchus—there is a discontinuity between the inferior oblique and the median oblique (line x-y in his figures) which is set quite far ven- trally, leaving much of the median oblique visible. In the course of evolution, the level of the discontinuity rises. The inferior oblique overlaps the median oblique and the latter is gradually reduced. Maurer relates this change to the growing dom- inance of the pectoral apparatus to which the inferior oblique is attached, and states that the Holocephali represent the extreme expression of this tendency. (He considers sharks but not batoids.) In Maurer's opin- ion, the Holocephali are also advanced in lacking a ventral rectus muscle of the sort that Chlamydoseloche shows. That shark has the two most ventral muscle bundles (c and d in Maurer's figures) rolled medi- ally to fonn a band bordering the midline. In the sharks, which Maurer regards as more highly developed, and in holocepha- lians this band does not appear. Through- out his paper, Maurer emphasizes the pro- gression from primitive selachians to Holo- cephali. It is clear that he r
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