ART. 14 FOSSIL AND EECEJSTT BEYOZOA CAISTU AND BASSLEE 153 



1923. Mamillopora tuberosa Canu and Bassler, North American Later Ter- 

 tiary and Quaternary Bryozoa. Bull. 125, U. S. National Museum; 

 p. 192, pi. 7, figs. 1-8 (not pi. 6, figs. 16-19). 



This species differs from the genotype in its much larger and more 

 constant mammillosities and in the presence of large hydrostatic cavi- 

 ties on the inner face. 



Occurrence. — Miocene (Bowden) ; Bowden, Jamaica. 



MAMILLOPORA CAVERNULOSA, new nrtine 



1919. Stichoporina tuberosa Canu and Bassler, Geology and Paleontology 

 of the West Indies Bryozoa. Publication Carnegie Institution, 

 Washington, No. 291, p. 98, pi. 1, figs. 20-23 (not pi. 7 and 6). 



1919. Stichoporina tuberosa Canu and Bassler, Geology and Paleontology 

 of the Panama Canal Zone Bryozoa. Bull. 103, U. S. National 

 Museum, p. 14, pi. 53, figs. 9-12. 



This species differs from the genotype in its smaller dimensions, 

 its finely punctated ovicell, and in the presence of numerous hydro- 

 static cavities on the inner face. 



Occurrence. — Miocene (Gatun formation); Banana River, Costa 

 Rica. 



mamillopora cupula Smitt, 1873 



Plate 26, Figures 3-13; text Figure 35 



1873. Mamillopora cupula Smitt, Floridan Bryozoa. Kongl. Svenska Vet- 

 enskaps Akademiens Handlingar, vol. 11, p. 33, pi. 7, figs. 146, 147 

 a-c. 



1919. Stichoporina tuberosa Canu and Bassler (part), Geology and Paleon- 

 tology of the West Indies Bryozoa. Publication Carnegie Insti- 

 tution, Washington, No. 291, p. 98, pi. 6, figs. 16-19 (not pi. 1 and 

 7 =Mamillopora cavernulosa and M. tuberosa). 



1923. Mamillopora tuberosa Canu and Bassler, North American Later Ter- 

 tiary and Quaternary Bryozoa. Bull. 125, U. i^ National Museumi 

 p. 192, pi. 6, figs. 16-19. 



Measurements. — Aperture of nonovicelled[^a = 0.14-0.20 mm. 



zooecia [Za = 0.10-0.14 mm. 



, ^ i. • n 1 • iha = 0.20 mm. 



Aperture oi ovicelled zooeciai, 

 ^ Ua = 0.16 mm. 



Structure. — The colonies have a discoidal or conical form. Their 



diameter is rather variable and measures 7 mm. at the maximum. 



One of our conical specimens was dredged alive, and although dry it 



preserved its ectocyst and its opercula and was then perfectly inclosed. 



Plunging it in water, it floats with the point on top but completely^ 



immersed with the point touching the surface of the liquid. This is 



then a floating species like Conescharellina, but its position is inversed. 



Each colony is a small hydrostatic apparatus utilizing the principle of 



Archimedes as well as capillarity and adapting itself easily to various 



bathymetric exigencies of the oceanic depths. The cupuliform 



colonies float with much more difficulty. 



