262 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 105 



mucro is nearest the orifice and nearest the midline but still diagonally 

 across from the anterior mucro. The posterior mucro is a bit to one 

 side of the back area of the external avicularium (pi. 14,C,K). The 

 anterior mucro, near the avicularial beak, is deflected away from the 

 midline. In heavily calchied or old specimens the external avicu- 

 larium may be deeply sunken and the mucros worn down or obliterated 

 (pi. 14,D). In the few fragments of this species, external avicularia 

 usually were present on the lower two or three rows of an internode 

 and generally absent from the upper rows of an internode. Whether 

 this is typical for the species or peculiar to the few fragments on hand 

 is not certain at present. However, this condition does not seem to 

 exist in the other five species. If an external avicularium is absent its 

 anterior mucro is also absent, leaving only the mucro nearest the 

 orifice. Dimensions of external avicularia: total length 0.144-0.187 

 mm. (average 0.169 mm.); total width 0.115-0.130 mm. (average 

 0.122 mm.); beak length 0.101-0.173 mm. (average 0.140 mm.); 

 back area length 0.050-0.072 mm. (average 0.058 mm.). 



Frontal oral ledge: At one side of the internal avicularial back 

 area is a frontal ledge (fl of pi. 14,K) that shows from the front or 

 outside as a partition across the base of the orifice (pi. 14,C,H,K). 

 In plate 14,E,F it is small and poorly developed. Cellarinella nutti is 

 intermediate between the two extremes, C. rossi and C. njegovanae, 

 in the angle that the oral ledge makes with the plane of the frontal I 

 surface. 



Orifice: The primary orifice is greater than a semicircle. Its 

 lower border is interrupted by the internal avicularium and the oral i 

 ledge. It is 0.173-0.216 mm. (average 0.193 mm.) long and 0.230- 

 0.259 mm. (average 0.246 mm.) wide. The secondary orifice is some- 

 what more orbicular (pi. 14,B) unless it begins to encompass some of i 

 the external avicularial zone (pi. 14, D). If nearly orbicular, and with- 

 out the external avicularium beneath, it measures 0.216-0.288 mm. 

 (average 0.233 mm.) long and 0.216-0.259 mm. (average 0.228 mm.) 

 wide. If it grows down to enclose part of the external avicularium, 

 as in plate 14, D, it measures 0.288-0.374 mm. (average 0.343 mm.) 

 long and 0.216-0.288 mm. (average 0.238 mm.) wide. 



Ovicell: Not observed. 



Types: Holotype, USNM 11231; paratypes, USNM 11232. {| 



Ecology: This species was collected at Antarctic Stations 44, 104, 

 and 234. No other species were growing on the colonies. 



Cellarinella njegovanae, new species 



Plates 15; 16,A-I 



Diagnosis: Zoarium bilaminate, nodulated, slablike and flattened. 

 Branching dichotomous. Internal avicularium obliquely placed below 



