192 Prof. M‘Intosh’s Notes from the 
borealis, Daudin, the twelfth species, and it swarms equally 
on the blades of the Fucit rocks and Laminarie in the south 
as on those in the north. ‘This species also has many 
synonyms, from the Serpula spirorbis, L., the Vermiculus 
exiguus albus nautiloides of Lister, the Planorbis minimus of 
Peters, to Spirorbis communis, S. reversa, S. baltica, and 
S. linnei of others. 
The collar is open as usual in the mid-dorsal line, but 
continuous ventrally, and it joins the membrane of the 
anterior setigerous region which De St. Jeseph has oceasion- 
ally found of a bluish tint. The membrane passes ventrally 
behind the last bristle-tuft and fuses with that of the opposite 
side. At the base of the branchiz are two minute eyes on 
the dorsum. 
The branchie are four on each side, each filament having 
a short, slender, and slightly tapered terminal process, and 
bearing from sixteen to twenty pairs of rather long ciliated 
and nearly cylindrical pinue, which do not arise quite opposite 
each other. Their colour is dull yellow, with a tinge of green 
from the blood-vessels. They are sensitive organs, receding 
with a jerk into the tube on being touched. 
The operculum, derived from the first left branchia, is 
saucer-shaped, with a massive peduncle, is calcareous and 
often infested by diatoms and other structures. De St. 
Joseph found Cothurina maritima growing on the operculum, 
and reproducing by fissiparity. 
The body is dark brown in front from the alimentary 
canal, reddish-orange posteriorly, aud 3 to 4 mm. in length. 
The anterior region has three bristled segments, the first 
series having characteristic tips. The first part of the 
posterior region of the body is not segmented, though 
ciliated, the total number of segments being 18-32, and 
terminated by the anus with a rounded papilla on each side. 
Each segment has two geniculate bristles. In the first 
segment are two excretory orgaus, from which ciliated canals 
join to form a single duct opening at the base of the 
branchie. 
De St. Joseph describes the alimentary apparatus as 
composed of an oesophagus in the anterior region, a large, 
brown cylindrical stomach immediately behind, followed by 
a sinuous intestine. He found spicules of sponges, diatoms, 
amongst others Sphenosira catena in the stomach, all pro- 
bably carried in by muddy currents. A blood-sinus encircles 
the canal, with lateral branches and ceca in each segment. 
The first bristles arise from a nearly cylindrical setigerous 
process, aud differ in detail from those of Spirorbis granu- 
