AND CLASSIFICATION OF THE HETEROPODA. 



19 



The visceral mass under protection of the shell is elevated, as it were, upon a 

 short pedicle springing from the dorsal region, at a point considerably posterior 

 to the swimming-fin. 



A row of reddish-tinted branchiae protrude beyond the mantle margin, and, as 

 in CardiaiJoda, the heart and intestine are distinctly visible through the shell 

 (Plate II. fig. M, b, d). 



The rachidian plates of Carinaria (Plate II. fig. 5, d, and fig. 6, o) are not 

 unlike those of Cardiapoda, but the dental processes in each are perfectly char- 

 acteristic. Thus, Carinaria is distinguished by three large subequal teeth, 

 flanked on each side by a rudimentary tubercle. 



The small internal tooth of the first pleural series is more highly developed 

 in Carinaria than in Oxygyrus ; and all the members of the pleurae (Plate II. fig. 

 6, 1, 2, 3.), are much stouter in the former than in the latter genus, though they 

 are somewhat exceeded in this respect by those of Cai^diapoda (Plate I. fig. 11, 



1, 2, 3.) 



REFERENCES TO THE FIGURES. 



PLATE I. 



Fig. 1. Firoloides. 



a. Tentacula. 



6. Eyes. 



c. Auditory sac. 



d. Buccal mass. 



e. CEsophagus. 

 /. Sucker-disc. 

 g. Swimming fin. 



h. Pedal ganglia. 



i. Heart. 

 k. Rectum. 



I. Vas deferens. 

 m. Bulbous portion of the 



penis. 

 n. Caudal appendage. 



Fig. 2. Head and Muzzle o/ Firoloides. 



a. Mouth. 



b. Lingual sac. 



c. Salivary glands. 



d. Buccal ganglia. 



e. Buccal artery. 

 /. Buccal nerves. 

 g. CEsophagus. 

 /}. Optic nerves. 



i. Cerebroid ganglia. 



k. Tentacles. 



I. Eyes. 



m. Auditory sacs. 



n. Nerve trunks connect- 

 ing i with the pedal 

 ganglia. 



0. Muscular sheath. 



Fig. 3. Pedal Ganglia and Great Vessels 

 of Firoloides. 



a. Pedal ganglia blended 

 together by their con- 

 tiguous surfaces, and 

 giving off nerves to 

 the foot and neigh- 

 bouring parts. 



6, Anterior division of 

 aorta. 



c. Pedal artery. 



d. Buccal artery. 



Fig. 4. Visceral Mass, Sfc, 



a. Great nerve supplying 



branches to the tail, 

 and connecting the I 

 pedal with the vis- 

 ceral ganglia. 



b. Anterior division of 



the aorta. 



c. (Esophagus. 



d. Cardiac ganglion 1 p 



e. Principal visceral gan- 



glion, sending a con- 

 spicuous nerve to 

 the mouth and its 

 sphincter muscle. 



/. Liver. 



g. Metapodium. 



A. Caudal appendage. s. 



i. Vagina. t 



k. Small leaflets or lobes u 



o/" Firoloides (female). 

 on the sides of the 5 

 opening. 

 , Oviduct. 

 , Flexure of I. t 



Oval opening of the 

 mouth. 



Anal aperture in front 

 of a ciliated papilla. 

 , And between, two little 

 leaflets like k. 



Ciliated elevation, with 

 depressed centre, pro- 

 bably a respiratory 

 organ. 



Little clusters of cells, 

 noticed at p. 8. 



Auricle of the heart. 



Ventricle. 



Muscular sheath. 



Fig. 5. Lingual Dentition of Firoloides. 

 0. Rachis. | 1-3. Pleuras. 



Fig. 6. Nidamental Chord q/" Firoloides. 



Fig. 7. Firola {considerably enlarged). 



a. Buccal mass. 



b. (Esophagus. 



c. Eye. 



d. Auditory sac. 



e. Pedal ganglia. 

 / Mesopodium. 



g. Swimming- fin 

 h. Penis. 

 i. Branchiae. 

 k. Visceral mass. 

 I. Metapodium. 



