258 Prof. W. King's Notes on Permian Fossils. 



a cellular or locular arrangement (a) in the plan of the vessels ; 



b, a large circular trunk circumscribing a " cell." 



Fig. 2 (b). A small jiortion of the same plexus from another situation. 



Fig. 3. Helix aspersa, removed from its shell : a, intesttnum rectum ; b, 

 ventricle of the heart ; c, auricle ; d, d', main pulmonary artery ; 

 k, secondary vessels of the pulmonary plexus [h) ; i, diaphragm 

 which divides the thorax from the abdomen {j) ; /, floor of 

 thorax, or respiratory chamber. 



Figs. 4 & 5. Helix aspersa, out of its shell. Fig. 4 shows the animal in the 

 act of creeping on the foot (d), and with the respiratory cavity (c) 

 in a state of inspiratory distension : a, orifice into the breathing- 

 chamber ; e', notch in edge of disk (e). Fig. 5 illustrates the same 

 animal, the foot being retracted, the respiratory chamber (c) col- 

 lapsed during expiration, and the orifice (a) being open to take in a 

 fresh svipply of air; e, the disk. 



Fig. 6. A portion of the vascular plexus from the roof of the pulmonary 

 chamber of Helix aspersa, showing the parallel disposition of the 

 secondary and ultimate vessels. 



Fig. 7- Animal of Lymneus stagnalis removed from its shell: a, siphon 

 in the projected state; b, c, respiratory chamber; e, heart; 

 g. denotes the position of the intestimim rectum ; /, gland of 

 the mucosity ; h, flattened ciliated tentacles. 



Fig.S.A. Muciparous gland oi Buccimtm nndatum: a, b, b, vesicles; 



c, intervesicular stroma ; d, cells from the interior of vesicles. 



B. A group of vesicles, seated on a peduncle, magnified : e, a vesicle ; 



b, the cells, containing the true secretion with which the vesicles 

 are filled ; /, ultimate cells. 



Fig. 9. Transverse section of the "colour-gland" of Buccinum undatum : 



c, lobules into which each lobe [b) is subdivided ; a, section of a 

 large vessel ; d, axis. 



Fig. 10. A lobule of the former section magnified: a, a, vesicles; b, 

 intervesicular stroma composed of coloured cells ; d, a small 

 portion further magnified ; c, ultimate cells. 



[To be continued.] 



XXT. — Notes on Permian Fossils : — Palliobranchiata. By 

 William King, Professor of Mineralogy and Geology in 

 Queen's University, Ireland (Q. C. Galway) ; Corresponding 

 Member of the Natural History and Medical Society of 

 Dresden, &c. 



[AVith a Plate.] 



Every palseontological fact connected with the Permian system 

 is of the highest interest. Apart from the many philosophical 

 questions pertaining to them, both this geological division and 

 its fossils are more intimately related to one of the great in- 

 dustrial resources of Britain than is generally imagined. The 

 Permian system, in point of fact, is the key to all our covered-up 

 coal-measures; and its organic remains are the wards of that 

 key. Should any one discover a bed containing Permian fossils, 



