200 Dr. J. E. Gray 07i a new genus and species of Seal. 



Plate X. 



Fiff. 7' Rectal branchiae of JEshna grandis, after M. Leon Dufour 8 

 C, a, orifices in the rectum of the branchial folds (A) ; a, dilated 

 extremities of the tracheae. 



Fig. 8. Head, tail, digestive system {d), tracheal (A) and bi-anchial {g) 

 systems, hepatic vessel (e), of Agrion Puella, after M. Dufour. 



Fig. 9. A small piece from the parietes of the intestine of the Cockroach, 

 showing the extreme distribution of the trachea (a). The blood- 

 cm-rent accompanies the tube only as far as i. The trachea then 

 describes a true network (e, c, d) of membranous tubes. In the; 

 meshes the glandular cells (/, g) are placed. A clear space inter- 

 venes between the trachea and glandular cells in which the nutri- 

 tive fluids, without the corpuscles, may probably move. 



Fig, 10. A small piece of the wing of the Cricket drawn under a high 

 power : a, a large trachea in the centre of the uervure or chan- 

 nel, surrounded by two opposed currents of blood (6, r) ; i, larger 

 branches; d, e,f, small terminal trachea?, entering alone, without 

 coincident, blood-currents into the scaly interval ; j, long, slender, 

 wavy trachea; floating in the fluid ; g, blood-corpuscles, travelUng 

 in the channel b. 



Fig. 1 1 . One of the tracheae from the scaly intervals between the nervures 

 of the wing of the Cricket, showing the mode in which it termi- 

 nates (6) between the scales d. 



Pig, 12. A minute portion of walls of the stomach of the Cockroach, show- 

 ing the wavy manner {c,f) in which the membranous capillaiy 

 tracheae are distributed around and between the ultimate glan- 

 dular elements ; at e, the current of the blood, as traced through 

 the blood-corpuscles, tvu'ns back : a, large spiral tracheae. 



Fig. 13. A small portion of a spiral trachea, exhibiting the coats under the 

 action of acetic acid : a, outer coat raised, indented like the spi- 

 ral (b) ; c, the internal or mucous coat. 



Fig, 14. A piece of voluntary muscle, re])resenting the manner in which 

 the tracheae enter the substance of the muscle. 



Fig. 15. One of the above tracheae traced into the substance of the muscle ; 

 a, b, c, network of ultimate membranous tracheae as they are dis- 

 tributed between the ultimate muscle-fibres — the latter being 

 omitted. 



[To be continued.] 



XIX. — Description of a new genus and species of Seal (Heliophoca 

 Atlantica)/rom Madeira. By Dr. J. E. Gray, F.ll.S., V.P.Z.S. 



&c. 



Some months ago J\Ir. MacAndrew most kindly procured for me 

 the skin of a Seal from the island of Madeira. A careful exami- 

 nation of it convinced me that it was a new species^ most allied 

 to Phoca harbata of the North Sea, but yet quite distinct from 

 it. Mr. MacAndrew after considerable trouble at length ob- 

 tained for me another skin of an older animal with its skull, 

 which proves that it is not only a new species, but presents a 

 new combination of characters such as 1 believe entitle it to be 



