248 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 105 



Radicles: The rootlets (pi. 9,M) are very thin-walled, tubular, 

 and usually of small diameter except for one which is unusually wide. 

 The diameters of these extremes, based on five readings, range from 

 0.072 to 0.547 mm. (average 0.202 mm.). The radicles grow prox- 

 imally, forming a tangled bundle below. 



Distribution: Thornely (1924, p. 9) described this species from 

 Commonwealth Bay, Station 11, 351 fathoms. The U. S. Navy 

 specimens came from Antarctic Station 44. 



Genus Melicerita Milne- Edwards, 1836 



Diagnosis: Colony erect, usually compressed or flattened, bilami-i; 

 nate, although in one species it may appear somewhat clavate and 

 slightly pinched in or nodulated here and there. Zooecia hexagonal 

 and arranged in transverse rows. Zooecial orifice crescent shaped, 

 wider than long and provided with two teeth or condyles, one neari 

 each proximal corner. In some species of this genus there may be 

 two more teeth, these latter placed on the distal wall of the orifice, 

 making a total of four. Avicularia are vicarious and good sized but ; 

 with comparatively small mandibles. Mandible arc shaped, very 

 short and much broader than long. 



The type species, as given by both Brown (1952) and Lagaaij 

 (1952) is Melicerita charlesworthii Milne-Edwards, 1836. 



Melicerita latilaminata, new species 



Plates 10, B- J; 11,A-F 



Diagnosis: Colony erect, calcareous, flattened, bilaminate, and' 

 dichotomously branched. Fronds broad. Cryptocyst beaded, trans- 

 lucent to opaque, depressed centrally. Modified parentheses lines 

 and cryptocyst ridges present. Thin, slightly salient mural rim. 

 Zooecial orifice broad, but short, and somewhat crescent shaped, with 1 

 two prominent blunt condyles, one near each proximal corner. Orifice 

 some distance away from the distal cornice. Ovicells endotoichal, 

 mconspicuous, placed distally to the orifice. Their pore is small and 

 crescent shaped. Avicularia large, but smaller than zooecia. Mandi- 

 ble a short wide arc, with a small median proximal tab which fits into 

 a small, similarly shaped notch in the avicularium. Radicles spring 

 from the front of some zooecia. Areolation hexagonal. The species, 

 is named for its broad flat fronds. j 



Colony: About 17 small fragments of this species are in the collec-i 

 tion, none of them very large and none a complete colony. The 

 largest fragment measures 17 mm. in length, and the widest region 

 of any fragment m.easures 9 mm. The "colonies" are nonencrusting. 

 They begin as a slender erect stalk from which radicles sprout down- 



