STRUCTURE OF THE CHONDRACANTHUS LOPHII. 71 



and Kkoyer. Rathke and Van Beneden have described only five ; but it is 

 probable that they had not examined fully formed individuals. Of these processes 

 four are much larger than the other three. Of the four large processes, the first 

 springs from the anterior margin of the second thoracic segment (the neck being 

 regarded as the first), the next two from the constrictions indicating the com- 

 mencement of the third and fourth segments, and the fourth from the extremity 

 of the fourth segment, from its attachment to the termination of which it pre- 

 sents the appearance of a tail. The three smaller processes arise intermediate to, 

 and are overlapped by, the larger processes when the animal is seen from the 

 dorsal aspect. The ventral mesial processes are only two in number, and corres- 

 pond in their position on this aspect to that of the second and third larger pro- 

 cesses on the dorsal aspect. Attached also to the ventral surface are two pairs of 

 feet (figs, 1, 2, dd). The first of these springs from the under surface of the neck 

 close to its junction with the head. It is situated a short distance behind the 

 last pair of foot-jaws. Its outer margin extends obliquely forwards towards the 

 cephalic lateral process, whilst the inner, much shorter, is continuous with the 

 corresponding margin of the opposite foot. The second pair arises farther back 

 from the posterior part of the second thoracic segment. Like the first pair, their 

 origin is oblique, so that the outer margin extends as far as the root of the great 

 lateral process of this segment, the inner being in close relation to the first ventral 

 process. Each foot is unequally bifid at its extremity, and presents, in addition, 

 four small tubercular elevations. 



The abdominal portion (fig. 2, g, fig. 8), very small, is situated between the 

 last lateral thoracic lappets, and is overlapped by the last dorsal mesial process. 

 It is distinctly divided into two segments, the proximal of which has connected 

 to its sides the two long strings of eggs (fig. 8, m) ; the distal projects between 

 these strings, and constitutes the true posterior end of the animal (fig. 8, n). 

 Attached to the sides of the ventral aspect of this terminal segment are two small 

 papillae, each of which is provided with a bulbous base. 



The alimentary canal commences at the mouth, and extends down the axis of 

 the cavity of the body (fig. 2, 7). It varies somewhat in length. In one specimen 

 we saw that it passed as far as the posterior end of the last thoracic segment, and 

 sent its lateral terminal coeca for a short distance into the lateral terminal lappets 

 of that segment. In another specimen the canal did not pass more than half way 

 down the last thoracic segment. In others,, to distances intermediate between 

 these extremes. The mouth opens into the oesophagus, which is a short tube, the 

 walls of which are almost free from dilatations, and the cavity of which is gene- 

 rally empty. The rest of the canal lies in the thoracic segment, and possesses 

 on its sides three pairs of distinct coeca, one pair being situated in each of the last 

 three thoracic segments. The canal between the first pair of coeca and the oeso- 

 phagus is much wider than the last-named part of the tube. The contracted 



VOL. XXIII. PART I. u 



