of Simple Ascidians. 361 
distinguished by many characters. Besides the very elongated 
form, the attachment is different, and the test is only slight] 
tuberculated ; the tentacular filaments are differently arranged, 
and the minute structure of the branchial sac is quite peculiar, 
and alone sufficient for specific distinction. 
Ascidia affinis, Alder & Hancock. 
Body elongated, ovate, tapering upwards, semitransparent, 
dirty greenish white; surface smooth or only slightly wrinkled, 
echinated and somewhat rugose towards the base and aper- 
tures. Apertures prominent, large, tubular, longitudinally 
ridged, rugose or echinated ; the branchial one terminal, the 
anal a little way down the ventral margin. Test semitrans- 
parent, thin, cartilaginous, of an obscure, pale, soiled greenis 
white, smooth above, and slightly roughened or echinated to- 
wards the base and tubes. Mantle pale olive-brown, almost 
colourless and transparent at the tubes, which are well-pro- 
duced, wide, and strongly ribbed longitudinally, both directed 
upwards. Tentacular filaments numerous, moderately stout, 
alternately large and small. Branchial sac minutely plicated ; 
papille only at the intersections of the meshes, thick, but ve 
slightly produced. Ventral plait wide, smooth or only slightly 
ribbed at the base, margin entire; the left oral appendages 
seven or eight, large, triangular, flattened, and denticulated. 
Length upwards of two inches. : 
Obtained in great abundance in Roach River, Essex, by 
Dr. Baird, when examining the state of the river to report on 
its suitableness for the maintenance of oyster-fisheries. They 
have usually a soiled appearance, and are much infested by 
parasitic zoophytes, and are generally united at the base into 
clusters, the base being considerably prolonged, forming a sort 
of irregular flat pedicle. 
Ascidia Normani, Alder & Hancock. 
Body elongated, pretty regularly oval, white, delicately 
fed id rap ash salou attached by the side of the base, 
transparent, strongly echinated, particularly towards the base 
and apertures, where the spines are usually compound. Aper- 
of a rose-colour, wide, produced, strongly ridged and 
echinated longitudinally ; the branchial one terminal, the anal 
about a third down the ventral margin; ocelli small, incon- 
spicuous. Test thin, transparent, white, or only slightly 
tinged with pale flesh-colour, covered with simple and com- 
pound spines, strongest towards the apertures an . 
Mantle delicate, of a pale buff flesh-colour or almost colourless; 
the tubes well produced, and of a rosy colour. Tentacular 
