664 THE MARINE ANNELIDES OP THE ORDER SERPULEA, 



and branchiae slightly exceed the thorax in length. The branchiae 

 are fifty in number with stout stems and rather short pinnules. 

 They are pink at the base, marked with purple and dark 

 green bands distally. The operculum (pi. XXXIL, fig. 9.) 

 with its peduncle is rather longer than the branchia?, being 

 about a quarter of an inch in total length. The peduncle 

 is dorso-ventrally compressed and becomes gradually broader 

 distally ; laterally it is fringed with a pair of delicate 

 wing-like expansions which are prolonged at the distal end of the 

 peduncle into short processes having the appearance of branchiae, 

 with a row of short processes or pinnules. The operculum proper 

 has the form of an irregular cone with the apex towards the 

 peduncle ; it presents on each side a low fold in line with the 

 wings of the peduncle ; the dorsal surface is flatter than the 

 ventral and is almost smooth ; the latter presents a few low 

 ridges radiating from the apex. The distal surface is nearly 

 transverse, almost circular in outline and slightly concave ; it 

 possesses three arborescent appendages attached near its centre 

 and diverging slightly from one another, each dividing dichoto- 

 mously to form a structure very like the horns of a deer ; the 

 terminal offshoots have the form of sharp spines. Very often the 

 three processes arise from a common stem ; sometimes there is 

 only an elevation of the distal surface of the operculum and from 

 this the three antler-like processes spring without being directly 

 connected with one another. In colour the operculum presents 

 variously arranged markings of green, crimson and white. 



There are seven segments in the thoracic region. The collarette 

 is an exceedingly wide and delicate membrane. The seta? of the 

 first segment of the thorax are very much longer than those of 

 the others. They are very indistinctly feathered on one side 

 towards the apex and taper to a very acute point. 



The abdominal seta? (pi. XXXIL, fig. 10) are quite unlike those 

 of the thorax. They are geniculate near the apex, the part of 

 the seta in the neighbourhood of the genu being slightly 

 expanded ; its concave border ornamented with about twenty 

 minute spinules, the apex extremely fine. The pectines of the 





