28

Scientific Memoirs by

notch between the dentations, and broadening out below, where it meets the
circlet of denticles guarding the actual entrance of the pharynx. These last
consist of a circlet of chitinous plates, rather larger than those of the triphine,
but of very irregular shape, especially those on the side opposite to the great
tooth.

      The male bursa copulatrix is, as will be seen from the figure, markedly
trilobed, the lateral lobes being rounded, while the median lobe is pointed,
though somewhat abruptly so. The ventral and ventro-lateral costæ form
a group almost exactly similar to that formed by the corresponding costæ of
the preceding species. The dorso-lateral consist of one large and one small
branch, which embrace between them the notch between the median and
lateral lobes; while the dorsal costæ are also represented by two branches, the
inner of which has a small rudimentary branch on its inner margin, rather nearer
its root than its point.

Sclerostomum tetracanthum Dies.

      Descriptions. —This species differs considerably from the preceding, and
is, in some respects, more nearly allied to Œsophagostoma columbianum, an
ovine parasite, to be described below, as the cause of nodular disease of the
intestine in sheep. This resemblance is most marked in the arrangement of
the parts about the external mouth opening; but, at the same time the two
species cannot be considered to be congeneric, as the present species has a
shallow, but at the same time distinct, buccal cup; whereas in Œsophagostoma
the armed peristome is followed immediately by the œsophagus.

      Diesing's¹description is as follows:—

      " CAPUT truncatum; oris limbo interno denticulis rectis densis, externo
aculeis 4 majoribus obtusis cruciatim dispositis armato.

      " CORPUS rectum utrinque attenuatum, bursa maris triloba, lobo intermedio
valde producto, lobis singulis multiradiatis, radiis furcatis; extremitate caudali
fœminœ recta, truncata, breve mucronata, apertura genitali supra caudœ apicem.
Copula sub angulo recto admissa. "

      This description is quite sufficient to identify the species; but, for purposes
of contrast with the other species, the following details may be added:—

      Cobbold²remarks:—

      " The fore-gut has a complicated structure, more strikingly so than has hitherto been
stated. The mouth leads into a strong buccal cup, supporting a circular series of short
bristles (described and figured by Schneider, but only indicated by a dark line in my
(Cobbold's) drawing), which separately have an extreme length of 1/760 of an inch. The
cup rests upon a muscular ring, which also supports a circular row (o¹in the present
figure) of small chitinous processes. The ring is succeeded by an anterior œsophageal
bulb the lumen of which is bordered by chitin plates (o²in the present figure).

      ¹DIESING: Loc. cit., Vol. II, page 305.

      ²DR. T. S. COBBOLD.—Journal Linn. Soc., London, XIX, 1886, pages 284—93. It is remarkable
that Cobbold in this paper, which I have recently obtained, with true and scientific insight, actually foretells
as probable some of the points established in the preceding paper.