250 PROCEEDINGS OF THE NATIONAL MUSEUM vol. los 



large orifice and operculum. The measurements of this very large 

 specimen are: over-all boxed-in operculum length 0.115 mm., width 

 0.317 mm. 



OvicELLS. These occur between the zooecial orifice and the distal 

 cornice of the frontal wall. Their shapes vary from oval to sub- 

 triangular, with frontal wall not much elevated above the level oi 

 the orifice and not higher than the mural rim. Dimensions: length 

 from 0.115 to 0.158 mm. (average 0.135 mm.); width from 0.166 

 to 0.230 mm.( average 0.194 mm.). The thin-walled, distally placed 

 ooeciopore is small and crescent shaped, measuring 0.022 to 0.043 mm. 

 (average 0.035 mm.) in length and from 0.086 to 0.101 mm. (average 

 0.095 mm.) in width. Its lower lip is beaded but its upper lip is not 

 (pl. 10,F). 



Avicularium: The avicularia are vicarious and not numerous. 

 Although good sized, they are not as large as the zooecia (pl. 11,D), 

 They measure from 0.346 to 0.490 mm. (average 0.423 mm.) in 

 length and from 0.245 to 0.403 mm. (average 0.292 mm.) in width. 

 The size of the opesia into which the mandible fits is 0.086 to 0.101 mm, 

 (average 0.097 mm.) long and from 0.144 to 0.187 mm. (average 

 0.167 mm.) wide. The chitinous mandible is wider than long, distally 

 curved in a broad shallow arc and provided with a straight proximal' 

 border from which a small median tab projects into the corresponding' 

 notch in the opesia (pis. 10,H; 11,E,F). The mandibular rim is 

 chitin-reinforced and a thinner circular area is present in the mid-.i^ 

 region of the mandible. 9 



Radicles: The rootlets are yellow to amber colored and trans 

 lucent; slender, cylindrical to gnarled, and rigid-walled. They sprout 

 from the frontal siu^face of the zoids and make their way toward th( 

 base of the colony (pl. 10,B,J). Their diameter is fairly uniforir 

 throughout, ranging from 0.058 to 0.076 mm. (average 0.072 mm.). 



Types: Holotype, USNM 11223; paratypes, USNM 11224. f p| 



Distribution: This species occurred at Antarctic Station 104 

 No other species were growing over the colony fragments, 



Melicerita obliqiia (Thornely) 



Plate 11,G-I 



Aspidostoma obliquum Thornely, 1924, pp. 16-17, fig. 4. 

 Pseudocellaria obliqua Livingstone, 1928, p. 42. 



Diagnosis: Colony flattened, nodulated, somewhat club shaped 

 Zooecia arranged in rows about it. Areolation and zooecia hexagonal 

 Crescentic orifice often placed obliquely, frontal depressed just be- 

 neath the lower lip. Operculum yellow and of same shape as the orifice 

 Cryptocyst and orifice rim granulated or beaded. Avicularia nol 

 observed. Ovicells large, imbedded between the two distal zooecia 



