284 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 14 



Spitzbergen to Greenland and south to the Gulf of St. Lawrence. 

 Point Barrow, Alaska, common down to 22 fms, G. E. MacGinitie, col- 

 lector, Arctic Research Laboratory. 



Frankly I am entirely at a loss to know where to place this remarkable 

 form. By its manner of growth, from the border inward producing a 

 secondary cover layer, the frontal appears to be a pleurocyst with large 

 areolar pores; the ovicell is endozooecial, opening beneath the closed 

 position of the operculum and extending into the proximal end of the 

 succeeding zooecium ; the operculum is heavily chitinized, simple, attached 

 without cardelles and straight across its proximal border where it is 

 broadly attached to the compensation sac and to which it adheres closely. 

 It does not conform to the aperture, there is a broad lunate thickening 

 near the distal end and one on each side but these do not appear to be 

 definite sclerites; muscles attached a little in from the border. The 

 proximal spinule of the aperture does not appear to be a useful character, 

 as it is very frequently wanting, but it is usually present on some of the 

 zooecia of every colony and rarely there are two or even three spinules 

 close together. 



The membrane to which the operculum is attached is somewhat 

 chitinized and covers the full width of the zooecial cavity like an anascan 

 ectocyst. If this is its true nature the frontal wall must be a pericyst of 

 a totally different nature from that of the Cribrimorpha. If it is true 

 that the anascan ectocyst has evolved into the floor of the compensation 

 sac, as has been suggested by several authors, there appear to have 

 been "attempts" by different methods in this direction by a number 

 of disassociated genera in addition to the Cribrimorpha, viz. Hiantopora, 

 Tremogasterina, Exechonella, Anexechona, Arachnopusia, and the pres- 

 ent genus, Hincksipora among the recent Cheilostomata. With our 

 present knowledge it seems futile to speculate on which, if any, of our 

 present genera are remnants of the stem group, or groups, which gave 

 rise to the Ascophora. It is even possible that there have been two lines 

 of evolution since some of the Ascophora have a simple operculum, 

 notably Umbonula and Rhamphostomella, and others a compound one. 



