The anatomy of the common squid, Loligo pealii, Lesueur . l ends of the rod-shaped cartilages are fastened to thelower part of the dorsal end of the upper jaw by means of muscle fibres whichradiate backward, inwaixl and forward from the jaw to the cartilage. The upper,i. e. the concave, side of each cartilage is covered, except at the end, by a trans-verse muscle which is several times as thick as the cartilage. The fibres of thismuscle are sufficiently curved to be concentric with the cartilage and arise from,and are attached to, a fascia which extends from one end of the fibres down-ward und
The anatomy of the common squid, Loligo pealii, Lesueur . l ends of the rod-shaped cartilages are fastened to thelower part of the dorsal end of the upper jaw by means of muscle fibres whichradiate backward, inwaixl and forward from the jaw to the cartilage. The upper,i. e. the concave, side of each cartilage is covered, except at the end, by a trans-verse muscle which is several times as thick as the cartilage. The fibres of thismuscle are sufficiently curved to be concentric with the cartilage and arise from,and are attached to, a fascia which extends from one end of the fibres down-ward under the cartilage and uji on the opposite side to the other end of thesame fibres. The only action which I can assign to this peculiar muscle is thatthe thickening of its fibres during contraction, presses downward the ends of theraduar cartilage, straightens it and thereby forces the radular forward. Theradular cartilages are connected by a sheet of muscle which stretches beneaththe radula]- retractors. A similar but thicker and narrower sheet of muscle. FiK. 12. 34 liilwcrii tlir cait ilasAvs al((i\c llic ladiila and radulai ivtrarlurs fDiiiis with theIdWiT nuisclc ail i)hh(|uel) cniiical lulic which contains the radular sac and overwhose apex the ra(hila,i inc^inbraiir is retlected. The radular retractors arise from I he dorsal end of tlic radular cartilagesand extending forward parallel Id lln Iadula are inserted near the venlral mdsof the cartilages upon the subiiulular nienibiane. Tile protractors of the radula arise from the lower edge of the upper jawand passing forward and inward are inserted upon the reflected distal end of thesuhradular uieiubrane. A small portion of the protim-tor is inserted upon thetoothless i»ortion of the same meniluanc which, it will be i-eniembered, coversthe sides and lop of the odontophore. Tlie alternate contraction of the retractorsand protractois draws the i-adula back and forth over the ventral end of theradular cartilages. The teeth art
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