REPORT OX THE PTEROPODA. 
23 
extending into the mantle. These muscles are probably constrictors of the pallial cavity ; 
and they have perhaps an influence on the successive dilatations of the kidney. It was 
these muscles which van Beneden 1 took for gills; but, as will subsequently appear, 
Cymbulia, like Clio, is destitute of these organs. 
The Digestive Tract. — The mouth is not as in the Cavoliniidse and Limacinidse 
(except Peraclis ) bordered by lateral lips ; here the lips are dorsal and ventral, and are 
produced along the sides of the proboscis to unite and become continuous with the dorsal 
margin of the fin. 
The horny portions of the buccal mass have already been described, notably by 
Troschel ; it is only necessary to note that the two jaws are situated more ventrally than 
in the Cavoliniidae. 
Into the buccal cavity open the two salivary glands (PI. IV. fig. 2, c) which, though 
readily visible, have not been noticed by any previous author. 
The oesophagus is very iarge (PI. IV. fig. 2, cl), and scarcely distinctly separable from 
the stomach ( e ). This latter contains within it the same large masticatory plates as in 
the Cavoliniidae ; the fifth posterior plate, though still triangular, differs a little in form, 
being very elongated. 
The stomach does not present at its posterior extremity a true caecum like that of 
Cavolinia and some species of Clio, but only a large and not very deep cul de sac. The 
intestine does not arise at the posterior extremity of the stomach but a little anterior 
to it. 
The liver is constituted like that of the typical Cavolinise ; according to Gegenbaur 2 
it opens into the stomach by from three to six canals. I have only been able to see, 
however, two of these hepatic ducts. This multiplicity of ducts among the Thecosomata 
is an archaic character, which the Cymbuliidse have retained. 
The intestine is longer and more coiled than in the preceding forms of Thecosomata, 
but morphologically the curvature is the same as in the Cavoliniidse. The intestine is 
entirely enveloped in the liver, only the extreme portion of the rectum being free. The 
anus is not situated so far to the left as in the Cavoliniidse, scarcely passing the 
median line, but the terminal part of the intestine is directed distinctly towards the 
left side. 
The Excretory and Circulatory Organs. — The kidney is situated on the dorsal aspect 
of the visceral mass, at the bottom of the pallial cavity. It is almost symmetrical in 
form and extends along the mantle, across both sides of the visceral cavity, in such a 
manner that when looked at in profile by reason of its transparency the lumen appears 
almost circular (PI. IV. fig. 1, h). The walls of this organ are exceedingly thin and 
transparent as in Clio. It opens into the pallial cavity by an oval aperture (m) surrounded 
1 Exercices Zootomiques, pi. i. fig. xii. b. 
2 Untersuchungen fiber Pteropoden und Heteropoden, p. 48. 
