. Introduction to zoology; a guide to the study of animals, for the use of secondary schools;. t the edges of the mantle andis forced out through the funnel,which lies between the eyes in (33. The shell is rudimentary in boththe squids and the cuttlefishes, andlike that of the slug is embedded inthe mantle. Even in Spirilla theshell, though coiled and containing asiphon, is completely covered by theskin of the animal. There are two liv-ing genera of Cephalopoda which havean external shell. One is an ally of FIG. iitt. — L<jiit/ Argonauta? which IS found in all tropical seas. The other
. Introduction to zoology; a guide to the study of animals, for the use of secondary schools;. t the edges of the mantle andis forced out through the funnel,which lies between the eyes in (33. The shell is rudimentary in boththe squids and the cuttlefishes, andlike that of the slug is embedded inthe mantle. Even in Spirilla theshell, though coiled and containing asiphon, is completely covered by theskin of the animal. There are two liv-ing genera of Cephalopoda which havean external shell. One is an ally of FIG. iitt. — L<jiit/ Argonauta? which IS found in all tropical seas. The other is the sole survivor of a once abundant group. This is the PearlyNautilus of the Indian and Pacific oceans. Its shell is di-vided into water-tight compartments, in the last formedof which the animal lies. It keeps its attachment tothe shell by means of a central strand of tissue — thesiphon (Fig. 164, s). Allied to the Nautilus is the huge a sailor in the THE SLUG AND ITS ALLIES 173 family of Ammonites, of which two thousand species areknown, ranging from the Silurian up to the Cretaceousformations.
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectzoology, bookyear1900
