BRYOZOA OF THE PHILIPPINE REGION 257 



We have chosen Smitt's species as a genotype because it is not 

 rare in the GuM of Mexico and the American students will be able to 

 more easily study its habits and anatomical characters. 



L( pnil 'in corrugata Waters, 1881, a beautiful fossil of the Australian 

 Miocene, should be classed in this genus. 



PETRALIELLA CRASSOCIRCA, new species 



Plate 23, figs. 4-9 



Description. — The zoarium is unilamellar. The zooecia are dis- 

 tinct, separated by a deep thread, a little elongated, large, rectangular; 

 the frontal is convex and covered with granules and with tremopores; 

 the distal portion is a large bipartite shield supporting two lateral 

 longitudinal, triangular avicularia with pivot. The aperture is 

 transverse; the wider poster is separated from the higher anter by 

 two lateral denticles; the peristome thin, very distinct from the 

 shield, is finely crenulated. The ovicell is hyperstomial, very globular, 

 finely punctuated. On the inferior face, each zooecium bears a distal 

 perforated area (0.10-0.20 mm. width). 



Measurements i — 



. \ha =0.25-0.27 mm. „ . fi2 = 1.10mm. 



Aperture,, or Zooecia , _ „_ 



[la =0.32-0.35 mm. \lz = 0.7d-0.85 mm 



Structure. — In the interior two lateral condyles separate the anter 



from the poster; the tremopores arc visible. On dead specimens the 



perforated area is often closed by a kind of chitinous operculum. 



Affinities. — This species differs from Petralia chitaJcensis Waters, 



1913, in its bipartite shield and in its straight and much smaller 



avicularia. It differs from Petralia dorsiporosa Busk, 1884, in the 



bipartite shield, in its longitudinal and not transverse avicularia, 



in its much larger shield, and in the presence of a cribriform area 



without other radicular pores. 



The specimen from Jolo bears 4 small radicular pores around the 



perforated area. 



Biology. — Almost all of our specimens were dead. They are more 



abundant in great depths of 250-300 meters. This species appears 



then to keep away from waters too warm. 



Occurrence. — 



D. 5137. Jolo Light, Jolo; 6° 04' 25" N.J 120° 58' 30" E.; 20 



fathoms; S. Sh. 



D. 5147. Suladc Island, Sulu Archipelago; 5° 41' 40" N.J 120° 



47' 10" E.; 21 fathoms; co. S., Sh. 



biavicularia Waters, 1887. Aperture, X 50. (After Waters, 1881.) U. Petraliella 

 biincisa Waters, 1882. Aperture, X50. (After Waters, 1889.) V. Petraliella 

 verrucosa Canu and Bassler. Operculum, X85. W. Petraliella crassocirca Canu 

 and Bassler. Operculum, X85. X. Petraliella echinata Canu and Bassler. 

 Operculum, X85. 



