80 PERCY SLADEN TRUST EXPEDITION 
10. Spirobranchus giganteus (Pallas) (Plate 8, fig. 6). 
Serpula gigantea, Pallas (89) 1766. 
Cymospira gigantea, Blainville (6) 1817; Schmarda (48) 1859; Quatrefages (42) 
1865. 
Spirobranchus giyanteus, Mirch (37) 1863; Benedict (3) 1886; Ehlers (15) 1887 ; 
Gravier (21) 1908. 
Specific characteristics : 1. Opercular plate with only two antler-like processes which 
sometimes however branch close to their bases. 2. Abdomen about 11 times as long as 
its greatest breadth and with numerous (200—300) segments. 
After studying numerous specimens which vary a great deal among themselves in 
unimportant details, these seem to be the only constant characteristics not mentioned 
among the generic ones. Ehlers (15) gives these with two other characteristics as 
distinguishing S. gigantea from S. incrassatus and S. tricornis, both of which have three 
processes, differently branched on their opercula, and from the measurements given their 
abdominal regions are only 4—7 times as long as broad. Ehler’s specimen of S. incrassatus 
seems however to have been a very small one. He gives the condition of the ventral lobe 
of the collar as another specific characteristic, pointing out that his specimens (? how 
many) of S. gigantea and S. incrassatus have this lobe divided into two triangular lappets, 
while in S. tricornis it is undivided and very elongated. At the same time he suggests 
that the condition with two lappets may be caused by damage. 
In the specimens that I have examined there seems to be no constancy at all with 
regard to the collar. The ventral lobe is in several cases (fig. 6a) folded inwards in the 
middle and gives a striking resemblance to two triangular lappets, but in only the one 
large specimen from Hulule, Male, are there two distinct triangular lappets which show 
no sign of having been possibly caused by the original lobe being torn. In a great many 
the whole ventral lobe is much shrunken and folded back as mentioned by Ehlers, and 
when unrolled no appearance of triangular lobes could be distinguished, though the collar 
appeared notched in the centre. 
The very numerous specimens of Pomatoceros triqueter from Plymouth that I have 
examined also show great variety as to their collars, and I am inclined to think that these 
are never of much use from a systematic point of view. 
In spite of Ehlers’ statement to the contrary, I have not found in any of the 
numerous specimens examined that all the collar setae were the simple blades which are 
constantly present to some extent in the collar fascicle of Serpulids. In some specimens 
however (fig. 6c) the characteristic ones approach that condition more nearly than in 
others (fig. 6b) where the hairy projection is larger. The one figured by Benedict 
(3, fig. 43) is very similar to the former. Gravier (21) does not mention the collar sete 
of his Red Sea specimens. 
Localities. Numerous specimens were obtained from the Zanzibar region in 10 
fathoms. One specimen came from Khor Dongonab, and several others also came from 
the Red Sea, having been obtained by divers in Suakin Harbour. 
In Prof. Stanley Gardiner’s collection there is a large and beautiful specimen from 
