208 



ASCIDIANS OF GUERNSEY. 



Post abdomen separated from abdomen by a constriction. Colony flat- 

 topped or lobulated ; colour amber. 

 Fragarium elegans (Giard). Castle Cornet, Terres Point, Alderney ; 

 common (Sharp). Colour rose red lined with white spots It lives in 

 crevices of the rock. 



Family IV.— DIDEMNIDiE (Giard). 

 Colony usually flat, thin and incrusting. Systems complicated and 

 irregular, inconspicuous or absent. Test with stellate calcareous spicules. 

 Testes single and large, vas deferens spirally coiled. 



LeptOClinum fulgldum {M.-Edw.) Bordeaux, Lihou and Terres Point 



(Sharp) . This forms small red patches under stones. 

 L. laeazii {Giard). Bordeaux, Cobo, Alderney; not very common (Sharp). 



Brilliant vermilion, forming patches of large size. 

 L. maeulatum {M.-Edw.) Common at many places, especially Terres 



Point and on Laminaria. Alderney (Sharp). This forms white and 



purple crusts. Vas deferens has 12 turns. 

 L. gelatinosum {M.-Edw.) Vazon, Havelet, Bordeaux, Alderney (Sharp). 



The only Leptoclinum whose substance is gelatinous. 

 L. aspemm {M.-Edw.) Vazon and Lihou (Sharp). This forms white and 



grey patches on stones, &c. 

 L. Listerianum (?). Vazon, Bordeaux and Lihou (Sharp). Forms grey, 



slimy crusts speckled with black and white 

 L. punetatum {Forbes). Bordeaux (Sharp). 



Family VII.-POLYSTYELIDJE (Herdman). 



Colony massive or incrusting. No common cloacal cavities present. 

 Ascidiozooids usually short bodied, large, rarely with a distinct abdomen. 

 Both apertures 4 lobed. Branchial sac large and well developed. Dorsal 

 lamina a plain membrane. 



Thylaeium normani {Alder). Bordeaux (Sharp). Ascidizooids with 



body divided into thorax and abdomen. Colonies formed of individuals 



projecting above the common fleshy base. 

 Synstyela Variegata {Alder). Lihou, Pleinmont Point (Sharp). Colony 



thin and incrusting. Ascidiozooids not divided into thorax and abdomen. 



Completely embedded in common test. 



Order II.— Thaliacea (Savigny). Sub-Order I.— Cyclomyaria (Krohn). 

 Family.— DOLIOLHXflE (Keferstein). 



Body free, more or less barrel -shaped ; branchial and atrial apertures 

 terminal and lobed. Mantle containing transverse muscle bands which 

 form hoops surrounding the body. Test rather slightly developed. 

 Doliolium dentieulatum {Quoy and Gaimard). In tow nettings in open 

 water, but never in the bays (Sinel). The development of this form is 

 most interesting. The egg develops into the usual tailed larva which 

 gives rise to what is called a " Nurse," which is asexual. This gives 

 rise to three types of buds from a stem or stolon. One is nutritive and 

 feeds the colony ; the second sets free animals called "Foster .Forms," 

 while the third is a sexual form which remains attached to the " Foster 

 forms " for a period and finally develops eggs. 



Sub-Order II.— Hemimyaria (Herdman). 

 Family I.— SALPID.32 (Forbes). 



Body free, elongated ; branchial and atrial apertures at the opposite 

 ends. Test well developed. Mantle with well-marked muscle bands which 

 do not form complete rings being wanting ventrally. 



