426 PROCEEDINGS OF THE NATIONAL MUSEUM vol. loi 



the papillae of the slightly developed fronds are scarce in some 

 places, more numerous in others; in the smaller specimens they 

 run out from more distinct fronds, which project as a fringe at 

 the outer rim of the ruff (visible on the larger specimen, too). 

 The 12 rovv^s of fronds corresponding to the 12 primary tentacles 

 are broader than the others and extended farther toward the 

 tentacles than the other rows. The 24 narrow rows are the short- 

 est. The sphincter is rather curious : in the part where the papillae 

 of the fronds are scarce (see above) there is only a diffuse 

 sphincter; in the part where they are numerous a unilateral, cir- 

 cumscribed, very fine and branched sphincter is present outside 

 the diffuse sphincter (fig. 79, h). There are about 48 tentacles. 

 They are conical and short, and their ectodermal, longitudinal 

 muscles are not strong. There are two broad siphonoglyphs sym- 

 metrically set, and 24 pairs of mesenteries, 2 of which are direc- 

 tives. The retractors of the mesenteries are strong, bandlike, those 

 of the directives more restricted. The parietobasilar muscles are 

 strong, forming a distinct, thick shelf on the mesenteries. The 

 nematocysts of the column are 15.5-19.7 by 2.5 jx (basitrichs) ; 

 those of the fronds 11.3-14 by 2-2.5 ^ (basitrichs) ; those of the 

 tentacles 14-26.8 by about 2-2.5 /a (in the larger specimen 14- 

 19 fi) (basitrichs) ; those of the actinopharynx partly 21-31 by 

 2.8-3.5 fx (basitrichs), partly 22.6-27.5 by 4.5-6.3 /* (microbasic 

 29-mastigophors) ; those of the filaments partly 25.4-46.5 by 2.8- 

 3.5 fjL (basitrichs), partly 21-28 by 5-5.6 /a (microbasic 2?-masti- 

 gophors) . 



Color in alcohol. — Pure white. 



Measurements. — The larger specimen (pi. 14, fig. 2), length 5 

 cm., breadth 2.6 cm. 



Collecting records. — El Mogote, sand flats, March 22, 1940, 2 

 specimens. 



Additional distribution record. — Panama. 



Remarks. — I have identified the specimens as bradleyi. A re- 

 examination of concinnata as well as of bradleyi is necessary, 

 however, in order to confirm my identification of the species de- 

 scribed here. 



Family AIPTASIOMORPHIDAE 



AIPTASIOMORPHA ELONGATA, new species 



Figure 80, a; Plate 14, Figure 8 



Pedal disc ordinarily developed. Column smooth, thin, with 

 visible insertions of the mesenteries (pi. 14, fig. 8). Cinclides, if 

 present, not set on elevations. In contraction of the animal up- 

 permost part of column drawn into the lower and forming a para- 



