PANAMA SPONGES — DE LAUBENFELS 463 



PLAKOOSA ELISA, new species 



Figure 45 



Holotype.—V.S.IS^M. no. 22237. 



The one specimen of this interesting species was collected inter- 

 tidally at Fort Randolph, It is an encrustation considerably less 

 than 1 mm thick and about 2 by 4 cm in lateral area. The color 

 in life was blue; the consistency is mediocre. The surface is min- 

 utely punctiform. The depressions here referred to are perhaps to 

 be interpreted as the location of pores. The entire surface is thickly 

 set with apertures about 200ai in diameter, one or more to the square 

 millimeter; which of these are exhalent and which inhalent cannot 

 readily be made out. The internal structure is densely fleshy, 

 except for the flagellate chambers, which are spherical, approxi- 

 mately 55/i in diameter. About them the spicales are densely 

 crowded. Those that are possibly to be interpreted as megascleres 

 are not much larger than microscleres. They are commonly siUceous 

 triaxons, with each ray approximately 2ijl by 25/i. Some of them 



Figure i5.—Plakoosa elisa, new genus and species: Spicules, X 666 (camera lueida). Only relatively 



abundant sorts are shown. 



may be described as sagittal with a very short rhabd or as a bent 

 oxea with a spine at the middle. Others have two spines at the 

 middle, as if they were reduced tetraxons. Still others are like 

 oxeas, with a bend in the middle that doubtless represents the place 

 where a hypothetical third or even fourth ray may have been placed. 

 All the megascleres may plausibly be interpreted as reduced tetraxons. 

 The microscleres bear a faint resemblance to asters, but although 

 they show much variation in shape, the following type is common: 

 There is an oxeote central shaft about 12/x long, from the middle of 

 which protrude one or more branches about 4iJ. or 5/x long, each of 

 which in turn has one or two branches only 1m or 2^ long. Each 

 ray is l/x or less in diameter. These might be further named, by 

 using the prefixes that are both applicable and customary, 

 "micromesoortho trichotriaenes . " 



