376 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 14 



Still these forms are different and can be separated usually without 

 much difficulty if the colonies are fully developed. Several of these 

 species occur in the Pleistocene, where they present just the same char- 

 acters shown by the recent specimens, e.g. californica, umbonata, and 

 vibraculifera, while ciliata is known as far back as the Miocene. It 

 appears evident that they are different and have been for a long time, 

 even though they do not show as sharp distinctions as are often found 

 in other genera. Fortunately most of them present more than one dis- 

 tinguishing character and I have been able to present the following key 

 which at least enables one to separate the forms named in the following 

 pages. I have listed most of them as species, as otherwise it would seem 

 necessary to regard all of them as varieties of ciliata. 



Key to the Species of Microporella 



1. Avicularia single, occasionally paired, proximal to ascopore . . 2 

 Avicularia paired, occasionally single, beside the ascopore . . 6 



2. Avicularium large with exceedingly long flagellum . vibraculifera 

 Avicularium smaller, mandible usually ending in a setose point 3 



3. Three umbos, 1 central, the others beside the aperture . umbonata 

 One umbo or none 4 



4. Aperture and ascopore surrounded by a high peristome which is 



bridged across its middle in fertile zooecia .... pontifica 

 The peristome not elevated 5 



5. Avicularium small, located in the lateral zooecial angle, the 



mandible setose, directed somewhat laterally . . . gibbosula 

 Avicularium larger, usually located on one side a little proximal 

 to the ascopore, mandible long triangular to setose (the variety 

 stellata with a stellate ascopore) ciliata 



6. Avicularia far forward beside aperture, mandibles setose, very 



long and directed forward parallel tractabilis 



Avicularia beside ascopore, mandible setose or lanceolate, not 

 unusually long, directed diagonally forward 7 



7. Ascopore surrounded proximally by an arcuate umbo of vary- 



ing size marsupiata 



Umbo, if present, pointed 8 



8. Mandible long-triangular, with a more or less setose point . . 9 

 Mandible setiform or long hastate 10 



