THE ANATOMY OF PLEUROTOMAEIA BEYHICHII. 265 



ciiiial muscle of gill-septum. /. p., I. p? Lateral oesophageal pouches. /. pr. 

 Lateral protractor. /.;•. Lateral retractor, w. Mouth. 7;/«. Mantle, vi.c. 

 Mantle cavity. ?;/.y. Mucous (hypobranchial) gland. m.g'.,m.g". Accessory 

 mucous glands, m. s. Mantle-slit. n. I. Nerve-layer in gill-septum, od. 

 Odontophore. o(/. f'., oi. c". Odontophoral cartilages. (3?. (Esophagus. o.>/. 

 Optic nerve, op. 1. Opercular lobe. os. Osphradium. oi. n. Otocyst nerve. 

 ovd. Oviduct. p\, p". First and second pedal nerves. ;;. r. k. Posterior lobe 

 of right kidney. ;;c. Pericardium, jo/. c. Pleural centre. ;)/.^. Pleuro-ptdal 

 connective, rd. iladula. r. Rectum, r. au. Right auricle, r. k. a. Right 

 kidney aperture, r. k. d. Right kidney duct. r. p. c. Reno-pericardial canal, 

 r. s. Radular sac. s. r. Supporting rods. sb. int. Subintestinal nerve, si. d. 

 Salivary duct. si. g. Salivary gland, sp. a. Supra-neural artery, sp. c. 

 S[)iral caecum, sp. int. Supra-intestinal nerve, st. Stomach, t. n. Tentacular 

 nerve, u. Ureter (right kidney duct), v. Ventricle, v. b. Vitreous body. 

 V. I. m. Ventral longitudinal muscle, v.pr. Ventral protractor, v. r. Ventral 

 retractor, v. s. Venous sinuses, v. t. m. Ventral transverse muscle. 

 The figures, unless otherwise stated, are of the natural size. 



PLATE 13. 



Figs. 1 — 12. Pleurotomaria Beyrichii. 



Fig. 1. — Anterior part of the body viewed from the left side, showing the 

 bifid left tentacle. 



Fig. 2. — Anterior part of the body viewed from above, to show dorsal 

 surface of foot. This specimen had lost its operculum. 



Fig. 3. — Opercular lobe of normal specimen. 



Fig. 4. — Oi)orculun). 



Fig. 5. — Dorsal wall of mantle cavity, with gills, mucous glands, and 

 rectum ; viewed from below. 



Fig. 6. — Dissection of the anterior part of the body; mantle divided and 

 reflected, floor of mantle cavity and dorsal surface of head removed, to show 

 the relations of the anterior viscera. 



Fig. 7. —General dissection from the right side, showing the mutual 

 relations of the alimentary canal, nervous system, heart, and pallial complex. 

 The forward extension of the right kidney is indicated by a brown shade. 



Fig. 8. — Side view of the buccal mass, showing the salivary gland with its 

 duct, the cerebral ganglia, and the buccal nerves. Enlarged. 



Fig. 9. — Dissection of the buccal cavity, showing the radula, jaws, and 

 horny papillae. 



Fig. 10. — Dissection of the buccal mass and crop : 1 and 2 the left, 3 and 

 4 the right oesophageal folds. 



Fig. 11. — Diagrammatic transverse section across the crop. 



