154 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



CALLOPORA TENUIROSTRIS Hincks, 1880. 

 Plate 29. figs. 10, 11. 



1879. Membranipora Flcmingi WATERS, On the Bryozoa of the Bay of Naples, Annals and 



Magazine of Natural History, ser. 5, vol. 3, p. 122, pi. 13, fig. 2. 



1880. Membranipora tenuirostris, HINCKS, General History of the Marine Polyzoa, I. 



Madeiran Polyzoa, Annals and Magazine of Natural History, ser. 5, vol. 6, 



p. 70, pi. 9, fig. 3. 

 1885. Membraniiiora tenuirostris WATERS, On the use of the avicularian mandible in the 



determination of Cheilostonaatons Bryozoa, Journal Royal Microscopical Society, 



ser. 2, vol. 5, p. 14, fig. 41. 

 1887. Membranipora trmiirostrlg HINCKS. Polyzoa of the Adriatic, Annals and Magazine of 



Natural History, ser. 5, vol. 19, p. 314. 

 1891. Membranipora tenuirostris WATERS, North Italian Bryozoa, Quarterly Journal of the 



Geological Society of London, vol. 47, p. 11. 

 1S98. Membraniiiora tenuirostris WATERS. Observations on Membra niporidae , Journal 



Linnean Society, London, Zoology, vol. 26, p. 685, pi. 47, fig. 7. 

 1909. CrassimarginatcUa ienuirostris NORMAN, The Polyzoa of Madeira and neighboring 



islands. Journal Linneau Society, London, Zoology, vol. 30, p. 288. 



Measurements. Opesia 



Ao=0.25-0.30 mm. . (7:3=0.40-0.45 mm. 



70=0.15 mm. ^ eeia l?3=0.20-0.25 mm. 



Norman has classified in the Crassimarginata group all of the Membranipores 

 having an interzooecial avicularium without consideration of the function of the 

 opercular valve which closes the ovicell in GrammeUa Crassimarginata Hincks. 

 The Crassimarginata group and Tenuirostris group are therefore quite distinct as 

 Waters has clearly shown in 1898. 



The frontal callosity of the ovicell is due to the incomplete development of 

 the upper calcareous layer (probably a pleurocyst). 



This species seems quite variable. From dreclgings at Oran (Algeria) two 

 sorts of specimens have been obtained which from all their characters may be 

 classed as this species. The first is large and vigorous, the zooecial dimensions 

 being 0.40 mm. by 0.60 mm. An analogous variation exists in the classic Helvetian 

 faluns of Touraine. The others are smaller and measure 0.40 by 0.30 mm., 

 dimensions which correspond to those in Waters's figure and which ought to be 

 considered as normal. Our specimens are simply a little narrower. 



The occurrence of this species as a fossil in America is entirely natural. It 

 lives at the present time at Madeira where the fauna is close to that of the Gulf of 

 Mexico. It has been found fossil in the Priabonian of Vicentin which is about 

 the horizon of the American Jacksonian. 



Figure 11 seems to represent the same species in the vicinity of the ancestrula, 

 indeed only the avicularia are a little different. 



Occurrence. Lower Jacksonian (Moodys marl) : Jackson, Mississippi (rare). 



Habitat. Mediterranean and Adriatic. East Atlantic: Madeira Islands. 

 East Pacific: Queen Charlotte Islands. At Naples, the species lives at depths rang- 

 ing from to 64 meters. 



