eleven and one quarter (11 ^4) inches ; thence to the termination of the base, six 

 (6) inches. 



The average dimensions of thirty-six (36) of the axes in the Museum of the 

 California Academy is five feet six and one third inches in length, and the diam- 

 eter of the largest, nine thirty-seconds of an inch ; diameter of smallest speci- 

 men, one sixteenth of an inch. 



Dr. Blake's specimens were preserved in a mixture of glycerine ana alcohol, 

 and the more delicate tissue of the polyps appears to have been_ somev/hat in- 

 jured by the latter ingredient. 



Additional specimens of the above species, from the same locality, have been 

 received from J S. Lawson, Esq., of the U. S. Coast Survey, by George Dav- 

 idson, Esq., President of the Academy. These latter were put in glycerine 

 only, and are in better condition than those received by Dr. Blake. 



Of the specimens received from Mr. Lawson, some individuals are younger 

 than either of Dr. Blake's. Tn these the polyp-rows are farther apart, and 

 there are not so many polyps in the row ; neither do the ends of the rows ap- 

 proximate so closely on the side opposite the axial edge ; the polyps being not 

 nearly so many in the same length, or presenting (as do some of Dr. Blake's 

 specimens) so crowded an appearance. In cross-section through the polypiferous 

 portions, the younger individuals are less oval or acutely-ovate than in the older 

 specimens. A comparison of individuals indicates an external diflerentiation, 

 analagous to that displayed by specimens of the same species in Virgularia. 

 The general aspect of this species, judging from the figure in Plate XXXI. of 

 Johnston's British Zoophytes (2d ed.), is like P. quadrangular is from Oban, on- 

 ly in that species the rows of polyps it is stated, are composed of " four, five 

 or six polyps in a row," one figure showing seven. 



