STYELOPSIS GLOMEEATA. 135 



them can generally be detected, and, with a little care, 

 an individual may be detached entire, showing 110 

 point of organic junction with the rest. The young 

 fix themselves on all parts of the older ones and in the 

 spaces between them, so that in process of time a 

 globular group as here described is the result. 



Genus 9. THYLACIUM V. Carus, 1851. 



Thylacium VICTOR CARUS in Proc. Ashmol. Soc. II [1851], 

 p. 266 ; [ALDER in Ann. Nat. Hist. (3) XI (1863), p. 167] .* 



Body elongated, oval, sessile, attached. Test cori- 

 aceous, opaque, adhering to the mantle. Apertures, 

 both four-lobed. Branchial sac with fewer than eight 

 folds, the meshes rectilinear. Tentacular filaments 

 simple, linear. Stomach and intestine on the right 

 side. Individuals associated by a creeping fibre on 

 a common base. Propagation by gemmae as well as 

 by ova (?). 



[The authors add : " The character to be revised," 

 and they quote the original description of Dr. T. V. 

 Carus, as follows :--] " Common base a broad fleshy 

 structure supporting closely-set individuals; outer tunic 

 coriaceous ; both orifices with four lobes ; abdomen as 

 long as the thorax." 



Dr. T. Victor Carus established the genus Thylacium, 

 which he formed for the reception of an Ascidian 

 found by him in the Scilly Islands, and to which he 

 also added the previously-known Ascidia aggregata of 

 Hathke. The apparent organic connection of the 

 individuals of this genus by a solid fleshy base has in- 

 duced the learned author to include it in the family 

 Clavelinida3, and to consider it to be propagated by 

 gemmation as well as by ova. This may be the case, 

 but the very close resemblance between the Thylacium 

 Sylvani and some of the smaller gregarious Cynthise 

 already described induces us to receive the opinion 



* For generic synonyms see iinder T. aggregatum and T. variolosum. 



