NOTOPLITES 353 



International Rules of Nomenclature a name once suppressed as a homonym cannot 

 be used again. The rule presumably applies here, and I therefore retain Hasenbank's 

 specific name. 



10. Notoplites crassiscutus sp.n. Figs. 12 E, 15 A, B, 16 A, B. 



Station distribution. Antarctic: Weddell Quadrant. Sts. 42, 160. 



Geographical distribution. South Georgia; Shag Rocks (Discovery). 



Holotype. St. 160, Shag Rocks. 



Description. Zoarium of the type characteristic of the genus, biserial (Fig. 15 A). 



Zooecia slender, with oval opesia and wide, more or less granular, cryptocyst (Fig. 

 15 A, B). 



Spines, three external, one internal. 



Scutum large and stout, proximal lobe usually the larger, lumen small, linear or with 

 a proximal arm at right angles, outer surface with striations radiating from stalk. 



Frontal avicularia small, often present on median zooecium (E), at bifurcation, some- 

 times on axillary zooecium (F or G), placed on portion proximal to joint (Fig. 12 E), 

 occasionally on other zooecia. 



Marginal avicularia absent. 



Basal avicularia (Figs. 12 E, 15 A, 16 A) at each bifurcation originating from zooecium 

 F (Harmer's lettering) with very long slender mandible directed from axil along basal 

 surface of branch in obliquely proximal, occasionally almost transverse, direction. 



Ovicells unknown. 



Remarks. In the specimen from St. 42 the lumen of the scutum tends to be more 

 extensive and the striations are less conspicuous than in the type, but there is a good 

 deal of variation, some scuta having lumina like those of the type specimen. In both 

 specimens there is considerable variation in the degree of granulation of the crypto- 

 cyst. The figured zooecia show the maximum and minimum. 



Notoplites crassiscutus appears to be more nearly related to N. elongatus (Busk) than 

 to other species. It differs from N. elongatus in the absence of marginal avicularia, in its 

 granular cryptocyst, and in its scutum, which is similar in shape, but has its lumen 

 greatly reduced and its frontal surface convex and radially striated. Like N. elongatus 

 var. calveti, N. crassiscutus has an axillary avicularium, with long slender mandible, 

 originating from zooecium F. In var. calveti the mandibular surface of this avicularium 

 is strongly convex, the opesia facing towards the frontal surface of the colony and the 

 mandible arching round so that its distal part lies along the basal surface of the branch 

 (Fig. 12 C, D) ; but in N. crassiscutus the mandible and opesia of the avicularium are not 

 visible in a frontal view, the mandibular surface being relatively flat and entirely on the 

 basal surface of the branch (Fig. 16 A), part of the chamber alone being visible in a 

 frontal view of the branch (Figs. 12 E, 15 A). Although the avicularium is larger, a 

 much smaller part of it is actually in the axil in N. crassiscutus than in var. calveti. The 

 mandible in N. crassiscutus is longer and may project beyond the margin of the branch. 



N. tenuis differs from N. crassiscutus in having longer zooecia of more uniform width ; 



