246 PROCEEDINGS OF THE NATIONAL MUSEUM vol. iob 



(average 0.288 mm.) while the width is from 0.173 to 0.288 mm. 

 (average 0.222 mm.). 



Aviculaeia: The avicularia (pi. 8,D-F) are vicarious, replacing an 

 autozoid in the regular transverse series. Their length is 0.619 to 

 1.101 mm. (average 0.796 mm.) and then- width is 0.331 to 0.432 

 mm. (average 0.400 mm.). They are a bit longer and narrower than 

 the autozoids, are diamond shaped, and have the beak directed 

 distally. The beak part occupies a considerable section of the 

 avicularian area and projects frontally. The rim of the proximal part 

 of the avicularium is raised and beaded, enclosing a flat, notched shelf 

 into which fits a chitinous peg from the mandible. The mandible 

 (pi. 9,A,C) is subtriangular in full face but the apex curves like a 

 sickle along the grooved beak. The proximal mandibular border is a 

 bit wavy and from it projects a chitinous peg. Along the midline is a 

 chitin-reinforced keel which terminates at one end in the sickled tipi 

 and at the other end divides into two chitinous sclerites which diverge 

 toward the two basal corners. The length of the mandible is fromi 

 0.518 to 0.691 mm. (average 0.606 mm.); the width is from 0.274 toi 

 0.346 mm. (average 0.307 mm.). 



Types: Holotype, USNM 11220; paratypes, USNM 11221. 



Distribution: This species was collected at Antarctic Stations 45 

 and 190. The specimen from Station 190 is a single, handsome, 

 dichotomously branching sprig, while Station 45 yielded only two 

 small fragments. Specimens were covered with fine algal debris. 



Mawsonia membranacea (Thornely) 



Plates 9,r-M; 10,A 



Cellaria membranacea Thornely, 1924, p. 9, fig. 2. 

 Mawsonia membranacea Livingstone, 1928, p. 39. 



Diagnosis: Colony club shaped. Zooecia arranged around the 

 stalk in irregular series of 10 or 11 in the present collection specimens. 

 Zooecial orifice as in genus. Salient cryptocyst ridges and chitinous 

 parenthesis lines present. Their end points do not meet at bottom. 

 Avicularia vicarious, as large as the autozoids. Mandible large, 

 keeled, falciform, triangular in face view, well reinforced with chitin, 

 and provided with a proximal median process. The mandibular keel 

 curved at the tip of the beak. OviceUs endotoichal, according to 

 Livingstone (1928, p. 39). 



Colony: This species is represented by a single, 9-mm.-long, 

 ivory colored, club-shaped fragment in the present collection. Its 

 proximal part is a mass of thin transparent chitinous rootlets. Areola- 

 tion of the colony is of the hexagonal type described by Hastings 

 (1946, p. 235). 



