154 
BULLETIN" 106, UNITED STATES NATIONAL MUSEUM. 
CALLOPOKA TENUIROSTRIS Hincks, 1880. 
Plate 29, figs. 10, 11. 
1879. Membranipora Flemingi Waters, On tlie Bryozoa of the Bay of Naples, Annals and 
Magazine of Natural History, ser. 5, vol. 3, p. 122, pi. 13, fig. 2. 
18S0. 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. Membranipora tenuirostris Waters, On the use of the avicularian mandible in the 
determination of Cheilostomatous Bryozoa, Journal Royal Microscopical Society, 
ser. 2, vol. 5, p. 14, fig. 41. 
1S87. Membranipora tenuirostris 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. 
189S. Membranipora tenuirostris Waters, Observations on Membraniporidae , Journal 
Linnean Society, London, Zoology, vol. 26, p. 685, pi. 47, fig. 7. 
1909. Grassimarginatella tenuirostris Norman, The Polyzoa of Madeira and neighboring 
islands, Journal Linnean Society, London, Zoology, vol. 30, p. 288. 
M easurements. — Opesia 
|/m=0.25-0.30 mm. 
1 7<9=0.15 mm. 
Zooecia 
J,£!= 0.40-0.45 mm. 
7,3=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 Grammella 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 dredgings 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 (Mooclys 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 0 to 64 meters. 
