STOMATOPORA JOHNSTONI. 431 



The main characteristic of this species is the very slender 

 habit, due to the disposition of the cells in series of 

 1-2 instead of 1-4, as in the preceding. In the 

 lower portions of the branches they are often ranged in 

 single line, the orifice rising alternately on opposite 

 sides ; above they form pairs, which are generally semi- 

 alternate, or single cells and pairs follow in regular suc- 

 cession. I have only met with the ooecia in a single case; 

 they form somewhat wedge-shaped and very ventricose 

 enlargements at the extremities of the branches, and 

 also at the bifurcation immediately below the terminal 

 branchlets. A large number of tubes (as many as fifteen 

 in one instance) are involved in them, and open out on the 

 surface. 



It is extremely difficult in this tribe to find valid spe- 

 cific distinctions ; but the present form seems to have a 

 fair amount of individuality, and can hardly be ranged 

 under any of our other British Stomatoporce. It is pro- 

 bably identical with the Criserpia Johnstoni of Heller; and 

 though, in the absence of a good figure, the determination 

 cannot be made with absolute certainty, I have thought it 

 better to adopt his name *. 



Habitat. On shells and stones. 



Localities. Guernsey (T. H.) : coast of Antrim 

 (Hyndman) . 



Geographical Distribution. On Anomia, Adriatic 

 (Heller) . 



* Heller's diagnosis is as follows: — "Stock kriechend, verastelt, die 

 rohrcnformigen Zellen zu zweien neben einaiider liegcud, alternireud ; Wan- 

 dungeu kornig." 



