NO. 2 OSBURN: eastern pacific BRYOZOA — CHEILOSTOMATA 425 



Among the species here dealt with there are two rather distinct 

 subdivisions, based especially on the form of the primary aperture. In 

 the first group, those like the genotype, R. costata Lorenz, there are 

 no cardelles and the proximal border is broadly arcuate (only modified 

 by the median lyrula, when this is present). In general these species 

 are also much more heavily calcified, the costules run up on the front 

 and frontal avicularia are often present. This group includes, besides 

 the genotype, R. scabra (Fabricius), R. fortissima Bidenkap, R. hincksi 

 Nordgaard, R. ovata (Smitt) and R. gigantea Osbum new species. 



The second group shows a very distinctive bisinuate outline of the 

 proximal border of the primary aperture, with a deep rounded "sinus" 

 on either side between the lyrula and the cardelles, which are usually 

 quite distinct. The frontal is usually plain, the wall is thinner, the 

 costules do not run up on the frontal, and frontal avicularia are 

 wanting. In this group are R. bilaminata (Hincks), R. spinigera Lorenz, 

 R. curvirostrata O'Donoghue, and R. townsendi Osburn new species. 



Probably R. ovata (Smitt), which has a perforated frontal and an 

 imperforate ovicell should be placed by itself, but R. gigantea also has 

 some additional frontal pores and there is much variation throughout 

 the group. 



Key to Species of Rhamphostomella 



1. Frontal pores present, ovicell imperforate 2 



Frontal with areolar pores only, ovicell with pores 3 



2. Zooecia of moderate size, frontal little granulated .... ovata 

 Zooecia very large (over 1 mm long), frontal excessively thick 



and rough gigantea 



3. Lyrula and cardelles both wanting ... hincksi 



Lyrula or cardelles or both present 4 



4. Lyrula and cardelles both present, proximal border of primary 



aperture bisinuate 5 



Lyrula present, cardelles wanting 9 



5. Oral spines present spinigera 



No oral spines 6 



6. Avicularian process high and flabellate, with a similar peristomial 



lappet opposite bilaminata 



No flabellate process opposite the avicularium 7 



7. Avicularian rostrum and mandible curved laterally across the 



aperture curvirostrata 



Rostrum and mandible shorter and not curved over the aperture 8 



