168 SPIO. 



m the division. The upper, as usual, are longer and more slender, but also present 

 indications of wings. The ventral lamella is separated from the dorsal by a notch with 

 a papilla, and is somewhat capstan-like, only the edges slope to a low cone in the centre 

 Its bristles curve downward and backward, taper to a fine point, and have narrow 

 wings (Plate CV, fig. 6). Moreover, they are all minutely dotted or dappled, and many 

 of the upper forms show a peculiar mark just below the tip, as if a portion had been 

 scooped out. It is possible that friction may be connected with this disappearance. 



The condition of the posterior region is unknown, but at the sixteenth foot the 

 superior lamella is still large and lanceolate, with a rounded outer or inferior margin, and 

 the bristles have rather increased in length. The ventral lamella, however, is smaller 

 and of the form of a short capstan. The bristles are also longer, and a ventral group of 

 four or five larger, longer, and boldly curved bristles is differentiated, each tapering to a 

 fine point, and the wings are more distinct. 



Genus XCVIIL— Spio, 0. Fabricius, 1785. 



Prostomium conical or rounded, without frontal processes ; eyes one or two pairs. 

 Pair of long tentacles (peristomial). Branchiae from the first setigerous segment to the 

 end and joined by laminae. Body filiform, pellucid, segments similar, proboscis partly 

 extrusible; unarmed. Anus furnished with cirri (quadrifurcate, (Ersted). Always two 

 rows of bristles which are capillary in the dorsal division. After a certain segment 

 (8th— 15th) the posterior row is formed of winged hooks. Tubes composed of 

 sand. 



0. Fabricius 1 in 1785 founded this genus for two annelids with two long tentacles, 

 formerly termed Nereis seticomis and N. filicornis, and his descriptions and figures aid 

 in clearing up the ambiguity which surrounds the species of Spio. Under the same head 

 Johnston 3 (1 838) included Nerine and Leucodore. (Ersted 8 (1844) retained the genera Spio 

 and Nerine, which he distinguished by the form of the dorsal lamellae thus :— Pinnis 

 lamellis instructis— Nerine ; Pinnis mamilla parva instructs— Spio. The genus Spio 

 is one of the genera of his Ariciae naidinae along with the genus just mentioned, 

 Leucodorum, and Disoma, He gives two minute species, S. seticomis and S. filicornis. 

 Yet those of Fabricius were 3 inches and 1 inch long respectively. Claparede 4 (1868) 

 showed that this distinction was artificial. He pointed out that in Spio the superior 

 lamella constitutes a lobe soldered to the base of the branchia or disappears completely. 

 Mesnil assumes that Malmgren complicated the question by reviving the generic name, 

 Scolecolepis, and undid the advances made by Claparede, a view which cannot now be 

 held. Yet he says that Malmgren conserved the genus Spio without definitely defining 

 it, and described under the name Spio filicornis, 0. Fabricius, a species which he (Mesnil) 

 has demonstrated to be very near his form, Spio Martinensis, and he doubts if Malmgren's 

 form is that of Fabricius, though the figure pertains to the same genus. He does not 



1 ' Gesellsch. natiirf . Freunde/ Bd. vi, p. 256. 



2 f Mag. Zool. and Bot./ vol. ii, p. 66. 



3 ' Arch. f. Naturges./ Bd. x, p. 103, 1844. 



4 'AnnelNap./p. 321. 



