NO. 1 OSBURN: eastern pacific BRYOZOA CHEILOSTOMATA 121 



on all of our genera except Tricellaria; spines are usually present at the 

 distal end, and a scutum (modified spine) usually protects the opesial 

 area. 



Key to Genera 



1. No dorsal vibracula or avicularia Tricellaria 



Dorsal vibracula or avicularia present 2 



2. Zoarium regularly provided with chitinous joints at a bifurca- 



tion, rarely a joint may be wanting Scrupocellaria 



Zoarium not regularly jointed, occasionally a joint may appear. . 3 



3. Zoarium biserial (occasionally triserial near the end of an inter- 



node) ; radicles forming a single bundle in the middle of the 



dorsal side Caberea 



Zoarium multiserial (usually, but see A. biseriata, new species) , 

 radicles forming two marginal bundles and leaving the me- 

 dian dorsal area free Amastigia 



Genus TRICELLARIA Fleming, 1828 

 This is Menipea, in part, of numerous authors, but is now separated 

 from that genus because of the difference in the manner of branching. 

 In Tricellaria the joint crosses the base of a branch far proximal to the 

 opesia of both outer and inner zooecia, while in JMenipea the opesia of 

 the inner zooecium is traversed by the joint, and there is no scutum. (See 

 Harmer, 1923.) 



The zoarium is erect and spreading, much branched, the internodes 

 typically consisting of 3 zooecia, but the distal branches especially often 

 have a larger number. The zooecia are usually much narrowed below 

 the opesia. There are no dorsal vibracula or avicularia and the radicles 

 are on the frontal side. The ovicells are hyperstomial. Genotype, Cellaria 

 ternata Ellis and Solander, 1786. 



Key to Species of Tricellaria 



1. Internodes usually with 3 ooecia 2 



Internodes longer, usually 5 or more zooecia 5 



2. Scutum attached well below the middle of the opesia 3 



Scutum attached at middle of opesia or above 4 



3. Scutum narrow, simple or with 1 to 3 points. . . . occidentalis 

 Scutum broader, 3 to 5 points var. catalinensis 



4. Joints light colored ; usually 3 outer and one or two inner spines. 



ternata 



Joints dark colored ; usually 2 outer and one inner spines. . pribilofi 



5. Zooecia elongate at base, slender gracilis 



Zooecia stouter and closely set, branches stiff 6 



6. A proximal scutum, no frontal avicularia, ovicell with a few 



large pores praescuta 



Scutum not proximal, frontal avicularia present, ovicells im- 

 perforate erecta 



