158 Transactions.— Zoology. 



ciliare. The lens is surrounded by a deep groove, so as to form practically 

 two lenses, the outer one being the smaller, the inner the larger and more 

 convex. It is in the groove of the lens that the fringe of the corpus ciliare 

 is attached. Within the eye is the fluid vitreous humour. The eye is 

 lined by a delicate layer of loose cells, underlaid by a pigment layer, and 

 then the inner layer of the retina. 



Behind the eyeball, and forming as it were a cushion at its base, is a 

 peculiar development of nervous tissue, the " white body." It consists of 

 rounded or irregular, apparently nucleated cells. 



Auditory Organs. 



In the substance of the cephalic cartilage are excavated two auditory 

 chambers, one on either side of the ridge already referred to. Their 

 walls give rise to several rounded protuberances, which are most 

 numerous on the side nearest to the nervous ring. The two cham- 

 bers approach each other on the posterior side, where the dividing wall 

 becomes thin and transparent. Each contains a single large otolith, 

 composed of carbonate of lime. The otoliths, (pi. viii., figs. 12-14) are 

 somewhat flattened, and are similar in shape, though one is a little larger 

 than the other. The main portion of the otolith has one of its margins 

 markedly convex, while the other is roughened and uneven, with two fairly 

 well-marked excavations. From this mass the otolith narrows to an end. 

 All the surface, except the roughened part referred to, is white and smooth 

 so far as can be seen with a pocket magnifier ; but the microscope shows 

 a rugose surface. 



EXPLANATION OF PLATES III.-VIII. 

 Plate III. — Sepioteuthis Mlineata. 



a, buccal membrane. 



b, " oreille externelle." 



Plate IV. — Dissection along posterior surface, showing position of organs. 



a, funnel. 

 b,b, hinge cartilages. 

 c,c, articular cartilages. 

 d,d, musculi retractores infundibuli. 



e, penis. 



/, intestine. 

 /', ink-sac. 

 g,g, branchiae. 



h. descending aorta. 

 v,v, veins from the mantle. 

 k,k, branchial hearts with appendages. 



I, ascending aorta with arterial branches. 



