MYSTIDES LIZZLE. Ill 



those of Mysta, which, however, has only two, and they are also of considerable thickness, 

 though tapered distally. They are much longer than those of Langerhans' Mystides 

 bidentata, which was also found by De St. Joseph at Dinard. 



Body about three inches in length, flattened, and with the segments distinctly marked 

 by a deep furrow anteriorly, and by a lozenge-shaped depression after the anterior third. 

 It is very slightly tapered anteriorly, but the diminution posteriorly is more pronounced. 

 The ventral surface has a median line anteriorly, and the segments are marked by 

 alternate elevated and depressed transverse bars, the former having an elevated and 

 projecting cushion or boss at each side. The specimens were in spirit before they were 

 observed, but three madder-brown or purplish bands could be distinguished. They 

 were incomplete posteriorly, and Theel's example also was apparently imperfect. 



The foot (Plate LXIX, figs. 11 [tenth] and 12 [fiftieth]) has superiorly a large reniform 

 cirrus of considerable thickness, having an umbricate arrangement, and being somewhat 

 cordate at the base. Its hypoderm is coarsely areolar and scarcely streaked. The 

 papilla supporting it is distinct. The anterior (e.g. tenth) differ from the posterior feet 

 chiefly in the tendency to form a point on the free dorsal edge, and in their smaller size. 

 The setigerous region is a strong bifid process, bevelled inferiorly, and bearing a series of 

 stout, translucent bristles, with a slight curvature distally. The dilatation at the tip 

 of the shaft is peculiar, presenting distally on each side a curved, hook-like spine directed 

 towards the serrated edge of the terminal blade, and with a denticulated margin beneath. 

 The other side of the distal end has a smaller spinous process (Plate LXXVII, fig. 20), 

 also with a slightly denticulated edge below it. The shoulder is not clearly seen in every 

 bristle, but it is distinct in those near the dorsal edge. The transparent terminal blade is 

 broad at the base, and gradually tapers to a long and fine point. The edge is minutely 

 serrated a considerable distance beyond the base. The minute structure of these bristles, 

 if they agree with the foregoing, is not clearly defined by Theel, but his species was 

 minute. 



The ventral cirrus is ovate or ovato-rectangular, barely reaching the tip of the 

 setigerous lobe at the tenth foot, but more nearly reaching it posteriorly where the tip is 

 less obtuse. 



The lamellas of the ' Porcupine ' example have a tendency to greater definition and 

 angularity. 



Reproduction. — The specimen from St. Andrews is a female, with the eggs fairly 

 developed, though not ripe, in February. De St. Joseph found a female of Mystides 

 bidentata, Langerhans, with natatory bristles from the sixty-sixth segment backward, 

 whilst the eggs were greenish. 



This form appears to fall under the genus Mystides of Theel, 1 a small example of 

 which came from Nova Zembla. The peculiar conformation of the first segment which 

 dorsally overlaps the head, the short lateral tentacles, the long tentacular cirri, the longer 

 dorsal cirri, and the structure of the bristles sufficiently distinguish it. Its comparatively 

 large size, in contrast with its northern relative, and the distinctive coloration are also 

 noteworthy. It is named after my sister, who procured it on the West Sands of 

 St. Andrews. 



1 ( K. Sc. Akacl. Handl./ Bd. xvi, 3, p. 35. 



