NO. 2 OSBURN : EASTERN PACIFIC BRYOZOA — CHEILOSTOMATA 457 



large, bulbous avicularian chamber at one side of the median line occupies 

 more than half of the frontal width, the rostrum elevated above the 

 aperture and directed laterally, both the rostrum and mandible strongly 

 hooked. 



Secondary calcification soon completely alters the appearance. The 

 front becomes very thick, v^rith short, heavy costal ridges, corrugations 

 and tuberosities. Frontal avicularia similar to the suboral, or w^ith an 

 acuminate mandible, variously oriented, are often abundantly developed. 

 The secondary peristome, formed by the thickening of the front wall, 

 usually develops a small uncinate process at the base of the avicularium, 

 opposite to this there is usually an erect pointed tubercle and between 

 these is a deep secondary sinus or spiramen; 2 or 3 additional pointed, 

 erect tubercles are often disposed around the oral border. The suboral 

 avicularium often becomes submerged within the peristome. There is so 

 much variation in the secondary calcification that scarcely any two 

 zooecia are exactly alike. 



The ovicell is about 0.20 mm wide, a little broader than long, the 

 ectooecial wall very thick, soon becoming deeply immersed: the exposed 

 "area" of the endooecial wall is semicircular, large, its dull white color 

 usually making it conspicuous, and with a very short, very wide labellum 

 only occasionally visible. 



Busk described the species from Mazatlan, Mexico, after which it 

 lay unrecognized in the literature for more than 70 years until Dr. 

 Hastings found it in the Crossland collections of the S. Y. "St. George" 

 from Panama and the Galapagos. In the meantime Smitt described 

 Cellepora verruculata from the Gulf of Mexico, and this name has 

 been applied to the western Atlantic form which occurs from southern 

 New England to Brazil. 



There can be little doubt as to the identity of the Atlantic and 

 Pacific specimens ; their measurements are practically identical ; both 

 have the semicircular frontal area on the ovicell ; they have the same form 

 of operculum with very minor variations in both ; the secondary calcifi- 

 cation is similar, and both have two similar types of frontal avicularia, 

 one with a slightly longer and more acuminate mandible than the other. 

 The "curved outline below the lucida" which Hastings mentions as a 

 "chief peculiarity" is present in Atlantic specimens from Puerto Rico 

 and Bermuda as well as in those from the Pacific ; there is some variation 

 in the width of the area but the ends are always broadly rounded and 

 quite different from the figures given by Hastings (plate 14, figs. 87, 88) 

 for the Mediterranean R. verruculata Waters. The operculum of the 



