No. 5] NEW OR CRITICAL CALCAREOUS ALGÆ. 19 



Thallus forming irregular, more or less extended, thin crusts 

 loosely connected with the substratum, with uneven, knotty sur- 

 face, or (f. iinbriccda) composed of small and irregular lamels, 

 irregularly imbricate or decussate, at length forming crust-complexes 

 up to 1.5 cm. thick. Conceptacles of sporangia prominent, at first 

 disk-shaped, then depressed in the central parts, 250—300 p^ in 

 diameter. Sporangia four-parted, 80— 90, w long and 25— 30/-/- broad. 



This species is closety related to L. Muelleri in habit, and in 

 part possesses forms similar to those in the latter. However, as 

 far as hitherto seen it does not form tubes surrounding other algæ. 

 The form umhonata grows in the same manner as specimens of 

 the said species attached to the root of other algæ, but I do not 

 know the nature of the substratum. The crust is thin, of irregular 

 shape, with distinct concentric striæ especialty in the lower part, 

 and the surface more or less uneven or knott}^ This uneveness 

 is in part caused bj' the shape of the substratum, and the knots 

 often by growing over extraneous objects. 



The form imbricata is composed of irregular crusts, or small 

 imbricate or sometimes even decussate lamels, now loosely con- 

 nected no w rather confluent, and at length forming crust-complexes 

 up to about 1.5 cm. in thickness. 



The conceptacles of sporangia are generally densely crowded 

 almost all over the surface, often so densely that the roofs be- 

 come angular. They are frequently prominent, at first disk shaped 

 or nearly so, then especially in f. umhonata more or less depressed 

 in the central parts, and here intersected with about 25 delicate 

 muciferous canals. The sporangia are four-parted, 80 — 93 y- long 

 and 25 — 30 p broad. The conceptacles do not seem to become 

 overgrown. 



ln structure the species also stands near to L. Muelleri, the 

 cells appear however generally to be a little shorter than in the latter. 



This species must be considered specificaily distinct from L. 

 Muelleri, the conceptacles being quite different, and no transitions 

 are to be seen in this respect. However, the material at my dis- 

 posal is too small to ascertain the mutual connection between the 

 two forms quoted which, on the one side, correspond with similar 



