ELASMOBRANCHS. 
1075 
sac, but bends forward in a pyloric part (to /). From 
the pylorus the duodenum runs straight back, and 
passes into the spiral intestine (Ji), which is continued 
by the short rectum. The mucous membrane of the 
intestinal canal differs in the various sections much as 
in the case of the Chondrosteans. In the oesophagus 
it forms longitudinal or, in addition, transverse folds, 
or is reticulated; or it may be studded with more or 
less hard papillae, pointed excrescences, in considerable 
number. The mucous membrane of the stomach is 
usually coursed by strongly developed (but few) longi- 
tudinal folds. The pyloric part, where there are also 
longitudinal folds of the mucous membrane, is some- 
times without internal limits, but sometimes bounded, 
both at the beginning and end, by an annular valve". 
As we have remarked above (p. 1052, note 5), the 
spiral intestine is usually regarded at the present day 
as a section of the duodenum. The spiral fold in its 
interior is very highly developed in the generality of 
the Elasmobranchs * * 6 , with reticulated mucous membrane 
and with transverse ridges on most of the coils. The 
rectum is short, and its mucous membrane smooth. 
The liver (fig. 301, c) is large and oily, usually 
consisting in the Sharks of two lobes, in the Rays of 
three. The gall-bladder lies free, or is embedded in the 
liver. The spleen ( x ) lies at the posterior part of the 
stomach. To the right thereof (vertically below / in 
the figure) lies the pancreas, which is usually of less 
volume. Into the beginning of the rectum there opens 
a digitiform gland (i), which was first remarked by 
Monro 0 under the name of vermiform appendage or 
coecal sac' 7 , but whose glandular, botryoid structure, 
around a central efferent duct, was first clearly de- 
scribed by Leydig 0 . 
There is no air-bladder. The kidneys (fig. 301, m) 
are situated as in the Teleosts. They taper in front 
and expand behind, sometimes so greatly that they 
seem to be confluent. Their general shape adapts itself 
to the external form of the body. Thus they are 
elongated in the Sharks, broader and shorter in the 
Rays. The urinary bladder is usually double, forming 
a dilatation of each ureter. The anterior part of each 
Fig. 301. Abdominal viscera of a male Shark. After Rymer- Jones. 
a, heart; b, gill-openings; c, c, c, lobes of the liver, the left removed, 
the middle ( lobulus Spiegelii ) and right retained; cl , oesophagus, pass- 
ing into the stomach ( e ), which is continued by the duodenum (/), 
into which the gall-duct (g) opens; h, spiral intestine; i, glandnla 
retroanalis ; 1c, urogenital cloaca; l , pterygopodium ; rn, left kidney; 
n, left testis; o, vas deferens; p, dilatation of the vas deferens ( vest - 
aula seminalis ); r , urogenital papilla; s, abdominal (peritoneal) pores; 
x, spleen. 
“ In the Basking Shark Blainville (1. c., p. 100, pi. 6, fig. 2, D) hence gave to this section the name of the third stomach. In 
the Picked Dog-fish I find no valve, either between the stomach and the pyloric part or between the latter and the duodenum. 
6 In a Picked Dog-fish I find 14 coils; Kroyer found 16 or 17. The last coil terminates in a broad, labiated fold. In several 
Sharks, however, the spiral fold is less developed. In Alopias vulpes and Carcharias glaucus it is described as very short. In Thalassorhi- 
nus vulpecula and Zygoma tudes no stair-like coils are formed along the inside of the intestine, but a long and broad membrane curves in 
cornet-shaped folds, one within the other, and lies like a packet within the intestine, with only one margin attached to the wall thereof. At 
the free margin of this membrane runs, according to Duvernoy (Ann. Sc. Nat., Zool., 2 ser., tome III, p. 274, pi. 10 and 11), a power- 
fully muscular venal trunk ( vena mesenterica ), which is continued by the vena porta and impels the blood and chyle into the latter. 
c Struct. Physiol. Fish., Edinb. 1785, PL II, 8; PI. III. E; PI. XI, D; PL XVIII, 16; PL XIX, 14. 
d Bursa cloacce , Retz., Ohs. Anat. Chondropt., p. 24. Glandnla retroanalis, Costa, Fna Regn. Nap., Chimeridei (1852), p. 36, 
tav. II, fig. 1 , g. 
e Beitr. mikr. Anat., Entwickel. Haien unci Rochen (1852), p. 56, § 38. 
