ANTIOPA. 



rather broad and expanded ; deeply grooved in front, and terminating in a point behind. 

 The aperture of the genital organs is placed near the middle of the right side. 



The single species on which this genus is founded occurs on the coast of Italy and on 

 the southern shores of England. It belongs to the Laminarian, and perhaps extends into the 

 coralline, zone; it is undoubtedly carnivorous, as we have taken from its stomach the 

 remains of some mollusk, probably that of a nudibranch. 



A detailed account of the anatomy of this genus has been published by M. Blanchard in 

 the 'Annates des Sciences Naturelles ;'* the following description of its internal structure, 

 however, is derived entirely from our own examination of specimens procured from both the 

 Mediterranean and the British shores; and it will be seen that, in several important 

 particulars, we are unfortunately at variance with that naturalist. 



The genus varies much in its anatomy from Eolis. The buccal mass (PL 43, figs. 1 a 

 and 2 a) is exceedingly large, a little depressed, and somewhat lozenge-shaped. The jaws 

 (figs. 3, 4) are likewise of great magnitude, and are not mere thin laminae; but are of 

 considerable thickness, of a triangular form, and each is furnished in front with a powerful 

 denticulated cutting plate (a), having, immediately within and parallel to it, another cutting 

 edge (b), which is plain. The tongue (fig. 5) is broad, and formed as in Boris, with the 

 posterior portion tubular. The spines (figs. 6, 7), which are simple, are, in A. crista ta, 

 arranged in thirty transverse rows, inclined forward, each row containing eighty spines, and 

 there is a central, equally large and plain spine in each row. 



The oesophagus (fig. 2 b) is wide, internally plicated, and very short ; it opens into a 

 distinct gastric pouch or stomach (c), placed in the anterior portion of the body. The stomach 

 is transversely elongated, and has the upper wall so thin and delicate, that the internal plica? 

 are distinctly seen' through it. On the lower portion, and towards the left side, where the 

 intestine leaves the stomach, there is a thin coating of a glandular structure (d). The 

 intestine (fig. 1 d, fig. 2 e) is very wide, and doubling back upon the stomach, passes 

 diagonally to the right side of the body, down which it is continued for some distance, and 

 then, dipping beneath the posterior lobe of the ovary, reaches the large anal nipple, (fig. 1 e, 

 fig. 2f) on the median line of the back near the posterior extremity. 



Two principal hepatic trunks open into the sides of the stomach above. On leaving that 

 viscus, these almost immediately divide into two branches; the anterior (fig. ^g,g) of which 

 pass round in front of the head, and are united on the median line. These two branches 

 communicate by various ramuscules, with the glands of the anterior papillae. The other or 

 posterior branches (k, h) of these hepatic trunks curve backward, and are connected in like 

 manner to the numerous papillae on the sides, extending more than half way down the body. 

 Here these branches terminate. The posterior papillae of both sides communicate with a 

 median trunk tube (i), which, dipping under the anterior ovarian lobe on the left side, passes 

 forward, and opens into the lower glandular aspect of the stomach, a little in advance of where 

 the intestine leaves it. All the principal trunks and branches are of a dark colour, when 

 the animal is alive. The median trunk tube corresponds to the great central hepatic duct 

 in Eolis, while the branches from the upper surface of the stomach are equivalent to the 

 anterior ones of that genus, which always open into the dorsal aspect of the digestive sac. 



* 3d Series, vol. x, p. 72. 



