98 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 17 



6. Thalli heavily calcified so that the color appears chalky 11 

 6. Thalli lightly calcified, at least in upper half, not chalky in 



superior aspect 7 



7. Tetrasporangial nemathecia more or less sunken, flush with the 

 surface of the vegetative thallus ; perithallus cells small, 4-20 fi 

 in greatest diameter from top to bottom of cell-rows 



P. pacifica 



7. Tetrasporangial nemathecia elevated; perithallus cells 5-60 //. 

 in greatest diameter from top to bottom of cell-rows . . 8 

 8. Paraphyses in tetrasporangial nemathecia of 10-18 cells, 

 the upper ones barrel shaped, catenate; rhizoids multi- 

 cellular P. guadalupensis 



8. Paraphyses in tetrasporangial nemathecia of 6-7 cells, the 

 upper ones not appearing catenate; rhizoids unicellular 



9 



9. Perithallus of erect (not ascending) cell rows; thallus loosely 



attached to the substrate ... P. rubra var. orien talis 



9. Perithallus of oblique or ascending cell-rows; thallus rather 



firmly attached to the substrate 10 



10. Thallus 70-100 /i thick; tetrasporangia 60-70 /x long; para- 

 physes non-clavate, short, coarse, of 5-6 more or less uni- 

 form cells P. conchicola 



10. Thallus 250-550 /a thick; tetrasporangia 60-100 /x long; 

 paraphyses slender-clavate, long, of about 7 elongated cells, 



the upper ones shorter P. mexicana 



11. Thalli to 450 /* thick; perithallus with conspicuous inter- 

 cellular spaces P. calcea 



11. Thalli 150-220 /x thick; perithallus without conspicuous inter- 

 cellular spaces P. clarionensis 



12. Thallus shrinking and splitting upon drying to form 

 numerous radiating fissures exposing the substrate 



C. fissurata 



12. Thallus not shrinking and splitting upon drying . . 13 

 13. Thallus heavily calcified, over 400 ju, thick; tetrasporangial 

 nemathecia immersed below the surface . . C. hancockii 

 13. Thallus lightly calcified, mostly under 300 jn thick; tetra- 

 sporangial nemathecia superficial 14 



14. Tetrasporangial nemathecia non-elevated, more or less 

 flush with vegetative surface; paraphj^ses coarse, little 

 differentiated ; tetrasporangia 40-45 jx long C. magdalenae 

 14. Tetrasporangial nemathecia elevated ; paraphyses slender- 

 clavate; tetrasporangia 60-80 /n long . . C. duhyi 



