120 MR. W. E. HOYLE ON THE [Mar. 5, 



preserved : in one the cartilage was sacrificed to the dissection of the 

 nervous system, and in the other it had already suffered a good deal 

 of mutilation. I made a sketch of the fragments put together as 

 carefully as possible, and afterwards compared this with the series of 

 sections through the head of one of the smaller specimens. The two 

 figures (Plate XIII. fig. 6) do not therefore represent a drawing of an 

 actual specimen, hut have been put together from these two sources. 



The basal portion of the cartilage, situated below and behind the 

 united pedal and visceral ganglia, consists of an oblong box with a 

 longitudinal septum down its middle. Each division is produced 

 backwards as a blunt prominence ; these are the receptacles in 

 which the auditory organs are lodged. Anteriorly the sides of this 

 box converge and the lower portion of the cartilage comes to consist 

 of a vertical keel, which splits at its lower margin into two plates 

 passing outwards and downwards below the eyeballs. These plates 

 are each perforated near their outer margin by a foramen (osp.), which 

 serves to transmit the nerve to the osphradium. At the point 

 where the sloping subocular plate joins the vertical keel is a large 

 foramen {v.f".), which serves for the passage of the veins from the 

 eyes into the large vena cava. Another foramen in the middle line 

 {v.f.) gives passage to the veins from the central nervous system. 

 From either side of the box a vertical plate is given off which lies 

 upon the posterior surface of each eye. The vertical sides of the 

 hox are produced upwards and support a horseshoe-shaped plate, 

 the concavity of which is directed backwards. The convexity extends 

 much further forwards than the vertical supporting plates, and arches 

 over a space in which the cerebral ganglia are situated ; its anterior 

 extremity is bluntly pointed. There are no basi-brachial cartilages 

 such as are seen in Sepia, but there is a thin plate of that material 

 in the dorsal wall of the vena cava behind the cephalic cartilage and 

 quite disconnected from it. 



The nuchal and siphono-articular cartilages (Plate XIII. fig. 7) 

 present no special characters worthy of note. The latter are of the 

 linear kind common to the greater number of Decapoda ; they 

 exhibit a tendency to a slight curve, in the form of y. 



Of more interest is the presence of a pair of cartilages in the 

 ventral wall of the siphon on its outer aspect. These are two thin 

 plates (Plate XIII. fig. 7) of the form roughly of an isosceles obtuse- 

 angled triangle, the median border being straight, the outer expanding 

 to an angle. The sheet of cartilage is thickest near the middle line 

 and thins out gradually towards the side, losing itself in the sur- 

 rounding tissues. Their formation had not commenced in the 

 smaller specimens; compare Plate XIII. fig. ft. 



The basi-pterygial cartilages had, however, developed to a con- 

 siderable extent in these examples. The extremity of the pen lies 

 in a groove between them. 



The pallial cartilages have a much more intimate connection with 

 the structure of the body-wall than seems to me to have been 

 hitherto recognized. The nuchal cartilage commences as a thin 

 plate which lies upon the muscles in the dorsal median line. Its 



