ART. 14 FOSSIL AND EECENT BEYOZOA CAISTU AND BASSLER 139 



HIPPOPORIDRA EDAX Busk, 1859 



Plate 22, Figures 1-4 



1873. Lepralia edax Smitt, Floridan Bryozoa. Kongl. Svenska Vetenskaps- 



Akademiens Handlingar, vol. 11. p. 63. 

 1889. Lepralia edax Jelly, A synomymic Catalogue of Marine Bryozoa, p. 



126. (Bibliography.) 

 1923. Cellepora minuta Canu and Bassler, North American Later Tertiary 



and Quaternary Bryozoa. Bull. 125, U. S. National Museum, p. 182> 



pi. 25, figs. 10-13. 



Measurements. — Apertural width = 0.06 mm. 



Structure. — Hincks, 1880, in introducing B.i'pjpoporidra calcarea 

 Smitt, 1873, into synonymy with Hippoporidra edax Busk, 1859, made 

 an error which rendered also problematical the synonymy of Miss 

 Jelly, 1889. Smitt (p. 64) has indicated the difference in writing that 

 the essential characters of the present species is the presence "of a 

 median umbo just proximally of the zooecial aperture." 



On our specimens the umbo is particularly constant on the salient 

 (superficial) zooecia; it is less apparent on the immersed (deep) 

 zooecia. 



The apertural width is exactly that indicated by Smitt. — 0.Q6 mm. 

 for the anter and 0.036 by 0.04 mm. for the poster. The frontal is 

 a granular pleurocyst surrounded by a single line of areolar pores 

 separated by short costules (as in Hinck's figure). The ovicell has 

 an identical structure, but the pleurocyst is incomplete and leaves a 

 very fragile olocystal area. The interzooecial avicularium is rather 

 rare; it always accompanies the groups of deep zooecia; its general 

 form is lozenge-shaped. The small frontal avicularium is always 

 placed on the line of areolar pores, but it is frequently wanting. 



The fossil form which we describe in 1923 under the name of 

 CeUepora minuta belongs to the present species. It presents, however, 

 some slight differences; the umbo is not constant and between the 

 costules there are sometimes, as in the fossil forms from the English 

 Pliocene figured by Busk, two or three areolar pores. The anter is 

 frequently almost as wide as the poster. The large interzooecial 

 avicularium has a form very similar to that of Hippoporidra calcarea 

 but with smaller dimensions. 



Biology. — The superb specimen that we have studied measures 

 6 cm. in length. It entirely covers a gastropod and emits two free 

 and symmetrically arranged lateral branches. It is ovicelled (Jan- 

 uary 30, 1885) . It is a case of symmetric symbiosis. 



Smitt's specimen was only a small fragment of 4 mm. in length, 

 "a little compressed, pointed of pumicose consistence." This is 

 the reason the small frontal avicularium can not be observed. 



