276 EXPERIMENTS AND OBSERVATIONS 
had recently spawned. Specimens are stated by Day to have been 
taken occasionally on the east coast and the south coast of Britain, but 
not very frequently. He mentions the record of one taken at Looe 
in 1843, of two in Mount’s Bay in 1844, and of one at a later date 
at Mevagissey by Mr. Dunn. This fish resembles the mackerel in 
many respects, the chief difference being that the scales are confined 
to a distinctly limited region behind the head, forming what is called 
a “ corselet.” 
Orcynus thynnus, Liitken, Thynnus thynnus, Ginther.—A specimen 
of the common tunny 3 feet long was brought to the Laboratory on 
September 19th. It was caught in mackerel drift-nets some miles 
from Plymouth Sound, only 18 mackerel being caught in the same 
haul. It was 3 feet long, and female. The ovaries were small, in an 
inactive condition, spawning having probably recently occurred. 
The eggs were very young. Dr. Bassett Smith examined the 
specimen for parasites, and found Brachilla thynni behind the 
pectoral fins, and a large number of Trematodes on the gills. The 
capture of a specimen of this species is not an unusual occurrence 
off the south-west coast in summer and autumn. 
Myliobatis aquila, Cuvier.—A single specimen of this species 
was brought to the Laboratory on November Ist, probably taken by 
a trawler, but the exact locality of its capture was not ascertained. 
It measured 62°5 cm. (2 feet 1 inch) across the pectorals, 40 cm. 
(1 foot 4 inches) from the snout to the end of the conjoined pelvic 
fins, and 65°5 cm. (2 feet 2 inches) was the length of the tail. 
I examined the viscera. ‘The left lobe of the liver was of great 
size and thickness, and covered the whole abdominal cavity ventrally, 
the right lobe was much smaller, and dorsal to the left. The 
stomach, intestine, spleen, and pancreas were as in other Elasmo- 
branchs. The contents of the stomach were much digested, but 
showed remains of molluscs: an operculate foot, apparently of 
Buccinum, a proboscis of the same, and some pieces of Pecten shell 
were recognised. The absence of claspers indicated that the 
specimen was female. The ovaries were smooth, extending nearly 
the whole length of the body cavity, broad and flat, and joined at 
their bases across the middle line. The eggs in process of matura- 
tion were visible, the specimen being apparently immature. The 
anterior ends of the oviducts with their openings were very distinct 
along the sides of the root of the liver just behind the pericardium, 
but the rest of the tubes were concealed beneath the pericardium. 
The posterior ends were dilated, and lay over the large kidney 
(metanephros). There was no distinct egg-shell gland. The 
species and the other members of the family are generally stated 
to be viviparous, and Couch’s account of the purse which he 
