382 MR. R. OWEN ON THE ANATOMY OF DISTOMA CLAVATUM. 
inch in breadth, exceeding that in the Hunterian collection by about one third; so 
that Pallas calls it the giant of its kind, ‘‘ad aliud quam Fasciolarum genus referre 
non potui, in quo quasi gigas erit.” 
The Distoma ventricosum of the ‘Synopsis Entozoorum’ of Rudolphi, is a minute 
species distinct from the Fasciola ventricosa of Pallas, whose account appears to have 
escaped the Lyncean eye of the learned founder of Entozoology. Pallas’s species is 
nevertheless characterized by Rudolphi, but under the designation of Distoma clavatum: 
and in the more detailed description contained in the ‘ Historia Entozoorum,’ reference 
is made to Mr. Menzies’ paper in the ‘ Linnean Transactions!,’ where the species de- 
scribed under the name of Fasciola clavata is evidently the same with the Fasciola ven- 
tricosa of Pallas. Mr. Menzies both describes and figures the posterior aperture ; and 
this testimony to the accuracy of Pallas is perhaps of more weight, as the author 
supposes that he is describing a new animal. Rudolphi, however, both in the ‘ Historia 
Entozoorum’ and in the ‘Synopsis Entozoorum,’ doubts the accuracy of this statement, 
and gives no account of the internal structure of the species. 
It was therefore with much satisfaction that I found, on looking over the admirable 
collection of Invertebrate Animals made by the late Rev. Lansdown Guilding, and recently 
sent to this country, a fine specimen of the Fasciola ventricosa seu clavata, of equal size 
with that figured by Pallas, and well preserved in spirit of wine. 
The circumstances under which it was originally obtained were not mentioned in the 
manuscript catalogue of Mr. Guilding. Pallas, with reference to the habitat of the spe- 
cies, merely states that his specimen was sent from Amboyna’. Mr. Menzies observes 
that he often found the Fasciola clavata in the maws of the Bonito, between the tropics 
in the Pacific Ocean. Rudolphi also assigns the stomach of Scomber Pelamys as the 
habitat of the Distoma clavatum, on the authority of Garsinus and Tilesius?. 
Mr. Guilding’s specimen of this large species of Distoma measures 2 inches 2 lines 
in length, and 2+ inches in circumference at the thickest part. It closely resembles in 
form the figure given by Pallas. Mr. Menzies, who observed the animal in its living 
state, represents it of a longer and more attenuated form. The outer integument is 
thin, crisp, and semitransparent, transversely and minutely wrinkled, and evidently 
fibrous in the same direction: it adheres but slightly, at least after maceration in spirit, 
to the succeeding layer. This tunic is evidently muscular, and composed of longitu- 
dinal fibres, and adheres pretty closely to the membrane immediately inclosing the cel- 
lular parenchyma of the body ; still, by proceeding carefully, they can be separated. 
The longitudinal fibrous tunic is beautifully ornamented with tortuous vessels, con- 
taining a dark-coloured fluid. 
The anterior orifice, which is the commencement of the true alimentary canal, is 
surrounded by a muscular sphincter, forming a suctorious disc or cup, of a firm and 
1 Vol. i. p. 187. Plate XVII. fig. 2. 
2 « Ex Amboyna missum fuit singulare hoc Molluscum.” 
3 It is always advisable to examine the stomach and intestines of the Bonito, Albicore, and other tropical 
Fishes, which are frequently infested with singular Entozoa. 
