BULLETIN 59, UNITED STATES NATIONAL MUSEUM. 163 



calii'ps occurrinif in tho dcpro.ssed intoi'veiiin<f areas. If tlio i-cticulum is of coarse 

 and open texture, probably becau.se of rapid j^rowth, tlie terniiiia! papilla' may be 

 rather larije nipples. 



Measureinetits of these structures are not iriveii. as the fiifures are natural size, 

 and they con\ey a correct idea. 



Repeated attempts were made to split this series of specimens into several species, 

 but evt>ry attempt led to the same result. There is one possibility by which a sepa- 

 ration mit;ht be affected. Those specimens that have only a small incrusting base 

 and early begin to produce ascending processes, and in which the papilhu have a more 

 pronounced tendency to assume the form of hoods, might be separable. But the 

 possibility of making such a separation is extremelv doubtful. 



Practically all of the variations of this species grow alongside one another, as at 

 Kaneohe, Oahu, therefore, so far as one can judge from the data at hand, the only 

 variation induced by environment is that greater depth retards growth. 



3. MONTIPORA TENUICAULIS, new species. 

 Plate LX, figs. 1, la, 2. 



Corallum I'amose; branches slender, terete or slightly compressed, of very nearly 

 the same diameter throughout their length, frequently anastomosing, tips tapering 

 or .somewhat swollen and blunt or flattened; when flattened, the tips give off lobes, 

 on which new calices appear, these lobes are incipient new branches. There is 

 some epitheca on the base of the branch used as the type. Length of specimen, SI 

 mm.; diameter at lower end, about 5.5 mm.; greater diameter at tip, 8.5 mm. 



Calices small; mayor may not be conspicuous; about0.5mm. in diameter; distiint, 

 1.5 mm. Septal arrangement ii'regular. Often the primary on the low(>r side is the 

 most cons))icuous septum, while the primary opposite may be next in size. The 

 calices frequently are plainly bilateral. There are usually two cycles; the cycles, 

 however, are not well differentiated, the greater number of the primaries may be 

 small, sometimes a few .secondaries may lie large. In some instances, however, 

 there are two regular cycles, a large and a small septum alternating. The septa are 

 composed of spines arranged in series one above another; the directive primaries 

 may be dentate lamelhe. 



Ccjenench\"ma on the tips of the branches loose, very porous; away from the 

 actively growing portion, with some pores hut rather compact. The transverse sec- 

 tion of tlie lower i-nd of the bi-atK h shows an inner, axial. V(>rv porous ]iortion. and 

 an outer, rather dense cortical portion. ai)out n.75 imn. in diameter. The surface of 

 the cnenenchyma is uneven, usually forming a lip or iiood on the lower side of each 

 calice. These hoods norTiialiy are low. al)out ••..", nun in height, diameter of the base 

 L.5 mm. Sometimes the surface may be plane: occasionally there may be a papilla, 

 round at tlie sununit. ■i..i rum. tall, and •_' nun. in diameter at the base. These tall 

 papilla' appear to lie iMcipi<'nt branches. The ctcnenchymal surface, examined more 

 minutely, is foiuid to be dt licately and ciowdedly spinulose. Phe s|)iiniles are slender, 

 wider at the base, the tips poinleii or bifurcated. Ne;n- the ends of the branches they 

 are more delicate than on the older [witions of the corallum. 



