654 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 14 



1 Idmonea atlantica van tenuis, Hincks, 1880:452. 

 Tubulipora atlantica var. flexuosa, Harmer, 1915:127. 

 Idmonea atlantica var. flexuosa, Osburn, 1940:333. 

 Idmidronea atlantica var. flexuosa Osburn, 1947:5. 



Pourtales gave only a brief description, in which the most important 

 points are the slender, flexuous and round branches. Smitt re-worked 

 Pourtales' material and gave a good description and figures. Unfor- 

 tunately, to the present time, no one has observed the complete ovicell 

 with ooeciostome. It is on the basis of the latter character, chiefly, that 

 1 am elevating it once more to full specific standing. 



The zoarium presents the same general characters as the well-known 

 atlantica, erect and branching from a small base, but the branches are 

 very slender, much flexed pnd sinuous, and in cross-section they are 

 round instead of being flattened on the dorsal surface. The fascicles are 

 short, the tubules 2 or 3 in series (rarely 1 or 4), while in atlantica they 

 are 3 or 4 to as many as 6, and they average a trifle smaller in diameter, 

 connate to the tips and slightly narrowed upward from the base. 



The ooecium and the ooeciostome (which is here described for the first 

 time) are quite different from those of atlantica. The ooecium is short, 

 usually occupying only two interfascicular areas, into which it spreads 

 more or less, while that of atlantica is usually very elongate and is 

 limited to the axis of the branches and not lobed laterally; the perfora- 

 tions of the ovicell wall also appear to be more minute and more numer- 

 ous. The ooeciostome presents the most striking difference, as it is very 

 short, erect, with a widely flared and rather thick border; it is located 

 just medial to the first tubule of a fascicle and slightly separated from it. 

 In atlantica the ooeciostome is about as tall as the tubules, curved distally, 

 expanded gradually, situated on the distal side at about the second tubule 

 of the fascicle, and its base connate with a tubule for a short distance ; 

 in the several ooeciostomes I have observed there is no intergradation. 



This form was described by Pourtales and by Smitt from north of 

 Cuba and later recovered by Osburn from Porto Rico and the southern 

 shore of the Caribbean Sea. Harmer's reference (1915:127) from the 

 Netherlands East Indies appears undoubtedly to be the same, for, while 

 he did not have a complete ooeciostome, his fig. 1, plate 10, shows the 

 base and pore in the characteristic position. Any attempt at a complete 

 synonjany would be useless, and it will even be uncertain whether Busk's 

 variety tenuis is the same as flexuosa until the ovicells are carefully 

 studied. Also, there is no certain record of Tubulipora (Idmonea) at- 

 lantica from the eastern Pacific. 



