96 PROFESSOR W. A. HERDMAN ON THE 



that Synstyela, Giard, has the prior claim and must be retained as the name of the 

 genus, even when, as happens to be the case, our knowledge of the internal characters 

 has been increased and the definition added to since the genus was originally created. 

 Consequently I must regard MICHAELSEN'S Allceocarpa zschaui as a Synstyela, and 

 furthermore I h'nd myself unable to distinguish it as a species from S. incrustans of 

 the Challenger Report. In MICHAELSEN'S " Revision der compositen Styeliden oder 

 Polyzoinen," * where both species are described, in his table on p. 73 he distinguishes 

 them by the proportions of the oviduct and the number of internal longitudinal bars in 

 the branchial sac, as follows : 



S. zschaui having the oviduct broader than long, and having sixteen to seventeen 



bars on each side ; and 

 S. incrustans having the oviduct longer than broad, and having twelve to fourteen 



bars on each side of the sac. 



Now, in the first place, with a soft, easily deformed structure like the oviduct it is 

 almost impossible to be sure of the true proportions ; and secondly, I find them varying 

 considerably in my specimens ; so that I cannot say they agree more in this character 

 with the one species than with the other. Then as to the number of longitudinal bars, 

 on dissecting out and mounting a branchial sac from a Scotia specimen I find the 

 number of bars to be fifteen on each side. According to MICHAELSEN, if it had sixteen 

 the species would be zschaui, and if it had fourteen it would be incrustans. Under 

 these circumstances, and as I find the specimens before me agree equally well with the 

 descriptions of these two species, 1 think there can be little doubt but that A. zschaui, 

 Michaelsen, is a synonym of Synstyela incrustans, Herdman. 



Diandrocarpa monocarpa (Sluiter) is certainly not the same species as Synstyela 

 incrustans, although it is probably a Synstyela. The number of longitudinal bars in 

 the branchial sac is very much smaller than in the present species. 



Family ASCIDIID^E. 



Ascidia charcoti, Sluiter. 



Locality. Station 325, in shore pool, Scotia Bay, South Orkneys, February 2, 

 1904. 



The single large Ascidia in the collection clearly belongs to SLUITER'S A. charcoti, 

 a species found by the Charcot Expedition to be abundant at " He Booth Wandel." 

 The Scotia specimen measures 8'5 x 5'5 x 2 cm., and was attached by a small area in 

 the middle of the left side. The branchial aperture has only seven lobes, a curious little 

 detail in which it agrees with SLUITER'S description. The atrial has the usual six lobes 

 characteristic of the genus. The test reaches a thickness of 2 to 3 mm., but has not 

 the red colour mentioned by SLUITER ; and the mantle is unusually thick and spongy 



* Milteilungen aus dem Naturhistor. Museum,, xxi., Hamburg, 1904. 

 (ROY. soc. KDIN. TRANS., VOL. XLVIII., 314.) 



