162 LAPHANIA. 



but the hook seems to differ from that of the species mentioned if one may judge from 

 the British examples. 



The posterior hump of the hook seems only to be fully developed in adult specimens, 

 as in a small example from Norway the posterior outline of the hook was straight except at 

 the lower end where the ligament was fixed, and this seemed to be less fused with the 

 base than in the adult. The posterior hooks did not show noteworthy differences from 

 those of the adult. In this example the body was terminated posteriorly by a large 

 rounded papilla budding out on each side from what apparently was a ruptured tail. 



The tube is massive, composed of a thin lining of secretion and a thick coating of mud 

 interspersed with minute stones and fragments of shells, generally arranged transversely. 

 The translucent fragments permit a certain amount of light to pass into the tube. In 

 some localities the tubes are formed of a thick layer of secretion and mud, amongst 

 which the small stones are carefully imbedded, and in several the smaller stones are 

 selected for the area near the transverse slit or valvular aperture. This end is elastic, 

 the slit forming a curve convex on one side and with a concave slope on the other, and 

 the symmetrical arrangement of the ends of the slit is noteworthy, a short fold at right 

 angles to the main slit occurring at each side. It is not yet proved that these tubes 

 found by the " Porcupine " of 1869 are those of Pista, since no trace of the inhabitant 

 was present. De St. Joseph found the tubes frequently on Rytiphloea pinastroides in 

 deep water, and composed of a transparent secretion covered with clear grains of sand 

 and pieces of algas. His species, however, differs. 



0. F. Midler's description and figures of this species are easily recognisable, especially 

 the figures. 



Montagu's figure of the annelid (by Miss D'Orville, 1808) shows two narrow tufts 

 of branchiaB, but is probably intended for this species. 



The Terebella maculata of Dalyell 1 (1853) somewhat resembles Pista cristata, but as 

 he does not refer to the minute structure of the branchias, which rather agree with those 

 of Nicolea venustula, especially if the " two pellucid stumps " represent traces of develop- 

 ing branchiaB, there is doubt, more especially as his Terebella pecten 2 agrees in regard 

 to the branchiao with a young Pista cristata. 



The Terebella flexuosa of Grube, 3 from Greenland, has only .a single pair of branchiae, 

 but they have a series of comparatively simple branches, and there are fifteen pairs of 

 setigerous processes instead of seventeen, as in Pista. 



De St. Joseph (1906) thought this form approached Thelepus setosus, De Quatrefages, 

 and gives reasons. 



Fauvel's 4 Bnpista dibranchiata has a hook very like that of P. cristata. 



Genus CL. — Laphania, Malmgren, 1865. 



Cephalic lobe truncated, with a horse-shoe-shaped plate over the mouth ; grooved 

 tentacles of moderate length. No eyes or branchiao. Buccal segment a little elongated 

 1 < Pow. Creat./ p. 203, pi. xxviii, figs. 10—13. 2 Op. cit., p. 208, pi. xxvi, fig. 9. 



3 < Archiv f. Naturges./ Bd. xxvi, p. 102, Taf . v, fig. 2. 



4 'Campag. Monaco/ p. 303, pi. xxviii, figs. 1 — 12. 



