528 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



Occurrence. — 



D. 5235. Nagubat Island, east coast of Mindanao; 9° 43' N.; 



125° 48' 15" E.; 44 fathoms; sft. M. (common). 

 D. 5478. Tacbuc Point, Leyte; 10° 46' 24" N.; 125° 16' 30" E.; 

 57 fathoms; Sh. 

 Cotypes.— Cat. No. 8339, U.S.N.M. 



CRISIA HORNESI Reuss, 1847 



Plate 78, figs. 10-13. 



1920. Crista hornesi Cantt and Bassler, North American Early Tertiary 

 Bryozoa, Bull. 106, U. S. National Museum, p. 704, pi. 141, figs. 1-4. 

 (Bibliography, geologic distribution.) 



Measurements. — Diameter of peristome, 0.08-0.10 mm.; distance 

 between apertures, 0.32-0.36.; width of segments, 0.32-0.36.; number 

 of tubes to segments, 16; and ovicell, 0.48 by 0.48. 



Affinities. — The micrometric measurements are identical with those 

 of Crisia denticulata Milne Edwards, 1838, but C. hornesi differs in 

 the presence of 16 tubes to the segments (instead of 11 as figured by 

 Milne-Edwards) and in the longitudinal keel ornamenting the 

 segments. 



The figure of Reuss, 1847, indicates 16 tubes to the segment; that 

 of Reuss, 1866 (incomplete), indicates 14 of them; those of Canu 

 and Bassler, 1920, indicate 17 or 18. Our present photographs indi- 

 cate 16. This constancy is remarkable and should be taken into 

 consideration. The figure of Manzoni, 1877, does not show the keel 

 and gives 21 tubes to the segment; it indicates certainly a distinct 

 variety. 



In Crisia denticulata Milne Edwards, 1838, there are only 11 tubes 

 to the segment although Harmer counted as many as 15. The de- 

 termination of Crisia from isolated segments presents great difficul- 

 ties. The illustration of the different variations on a living colony is 

 still to be made. 



Biology. — According to Harmer the full development of Crisia on 

 the English shores is in April and May. Our ovicelled specimens 

 were collected in September. 



Occurrence. — 



D. 5478. Tacbuc Point, Leyte; 10° 46' 24" N.; 125° 16' 30" E.; 



57 fathoms; Sh. 

 D. 5580. Sibutu Island, Darvel Bay, Borneo; 4° 52' 45" N.; 

 119° 6' 45" E.; 162 fathoms; br. S., co.; 11.2° C. 



Plesioty pes. —Cat. Nos. 8340, 8341, U.S.N.M. 



