466 THE ANIMAL KINGDOM. 



Fossil Cephalopoda, Zittel, Handbuch der Palaeontologie, Abth. I. ii. Th. 3. 

 1884; Genera of Fossil Cephalopoda, Hyatt, Proc. Boston Soc. Nat. Hist. xxii. 

 1882-83. Development of shell in do., Branco, Palaeontographica (N.S.), 26 and 27, 

 1879-81. Relation of Ammonites, Munier-Chalmas, &c. C. R. 77, 1873. Am- 

 monites, composition of shell, Suess, SB. Akad. Wien, Ixi. Abth. i. 1870. 



CLASS SCAPHOPODA. 

 (Solenoconcha ; Prosopocephala). 



Glossophorous Mollusca, with a shell shaped like an Elephant's tusk, 

 and open at both ends, the small as well as the large. Its concave side is 

 dorsal, the convex ventral. The mantle, which lines the shell, arises in the 

 larva as a right and left dorsal fold, which grow towards the ventral aspect, 

 and fuse one with the other, except for a short distance, in front and 

 behind. The tube thus formed extends both backwards and forwards over 

 the animal. The shell developes in a corresponding manner, and is at first 

 incomplete ventrally. The head is cylindrical, and bears the mouth at its 

 extremity, surrounded by a circle of tentacles. Two pads, one right, the 

 other left, at the base of the head and above the foot, give origin to a 

 number of ciliated contractile processes, terminated by flat expansions. 

 It is possible that they represent the ctenidia. The foot is long, and trifid 

 at its extremity. 



The nervous system consists of a pair of cerebral ganglia, united by 

 long connectives to a pair of pedal ganglia, to which the pleural ganglia are 

 closely apposed. The visceral loop is long, and placed below, i.e. in front 

 of the anus. There are no eyes, but a pair of otocysts is attached to the 

 pedal ganglia. The digestive tract possesses a buccal mass, inclosing a 

 radula armed with five longitudinal rows of simple teeth. The alimentary 

 canal consists of an oesophagus, a short stomach, into which open two large 

 symmetrically placed liver lobes, an intestine, which forms several coils and 

 finally opens on the ventral surface in the middle line. There is no heart. 

 The coelome consists of a series of channels and sinuses, and is filled by 

 a colourless blood. There are two nephridial openings, one on each side 

 the anus. The nephridial chamber is perforated by the intestine, and is 

 beset with a number of small caeca. The genital gland lies clorsally. It is 

 alike in both sexes, and consists of a median tube bearing three rows of 

 caeca one dorsal, two lateral. The duct opens into the nephridial sac on 

 the right side. 



Segmentation is unequal, the gastrula invaginate. There are three 

 ciliated rings surrounding the body in front of the mouth, and representing 

 the velum. The body lengthens behind the ciliated rings. There is a 



