178 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 12 



The growth habit of this beautiful species is very striking, but not 

 unique. In its earlier stages it is represented by parallel forms in both 

 Lithophyllum and Lithothamnium, in which latter genus L. lichenoides 

 f. agariciformis (Johnst.) Foslie (1929, p. 43, pi. 11, fig. 9) has a very 

 close superficial resemblance. In Lithophyllum the closest similarities are 

 seen in L. expansum Phil. (Mediterranean), L. decussatum (Ell. & Sol.) 

 Phil. (Mediterranean) and L. Diguetii (Hariot) Heydrich (Gulf of 

 California). The latter appears to be a smaller plant, with little tendency 

 to form chambers when mature; but, if it should prove to be a reduced 

 northern form of the plant here under consideration, the name Diguetii 

 has priority of about six years (Hariot 1895, p. 168). 



This Lithophyllum grows on rocks in the surf near low tide line, and 

 the primary thallus forms a cap on top of a rock, or projects as a bracket 

 along its edge. In its primary stage it is more or less horizontal, similar 

 in aspect to a bracket-fungus. The edge is subsimple to irregularly crenate, 

 the surface flat to undulating, smooth but dull, the lower surface white, 

 the upper more roseate. It may increase to a radius of 3-8 cm or even 

 more before developing any chambers, and may become abundantly fertile, 

 with the conceptacles chiefly on the under surface. Then erect projections 

 occur on the upper surface, terete and tapering or ligulate, and these, at 

 first scattered, become broader and flatter and meet, though they reach a 

 centimeter or more in height before continuity is achieved, and the height 

 of the upper margins of the chambers is by no means uniform. The thallus 

 may reach a height of 6 cm, perhaps more, and a diameter of 15 cm or 

 more; but, since these measurements were made upon specimens in the 

 laboratoiy and since it is extremely difficult to remove the large ones 

 intact from the rocks, it is probable that they become much broader. The 

 chambers vary a great deal in size and in shape. They may be from 3 mm 

 to 20 mm in diameter, most commonly somewhat less than 10 mm. They 

 may reach a depth of 3 cm, but in thicker thalli they are commonly con- 

 stricted or cut off by more or less complete secondary horizontal septa, 

 so that a clear depth of the whole thickness to the horizontal layer is 

 rarely seen in these larger specimens. While the growth of the chambers 

 is entirely discontinuous in early stages, in large individuals they seem to 

 start with more continuous ridges near the margin and to rise gradually, 

 though even in old plants separate submarginal ligulate projections are 

 common. The horizontal thallus may reach a thickness of 3-5 mm in the 

 earlier growth phase, but in old plants it commonly disappears from the 

 central portion, probably by the action of penetrating algae and worms, 

 leavmg a complex irregularly perforate mass. Occasionally near the over- 

 hanging edge pendant, as well as erect blades, are formed. Old thalli may 



