124 THE SPONGES. 



Previously known distribution of P. similis. Petrosia similis : South of Cape 

 of Good Hope (Lat. 35° 4' S., Long. 18° 37' E.) at depth of 150 fath. ; be- 

 tween Kerguelen and Heard Island (Lat. 52° 4' S., Long. 71° 22' E.) at 150 

 fath. P. similis var. massa : between Strait of Magellan and Falkland 

 Islands (Lat. 51° 35' S., Long. 65° 39' W.) at 70 fath. P. similis var. com- 

 pacta: Philippine Islands (Lat. 11° 37' N., Long. 123° 31' E.) at 18 fath. 



Pachychalina 0. Sciimidt. 



1SG8. Paaht/chalina O. Schmidt, 1868, p. 8. 



1887. Paehychalim O. Schm., Vosmaer, 1887, p. 342. 



1887. " " Ridley and Deiidy, 1887, p. 19. 



1890. " " Dendy, 1890, p. 353. 



1894. " " Dendy, 1894, p. 240. 



1902. " " Lundbeck, 1902, p. 5. 



Pachychalina acapulcensis, sp. nov. 



Plate 16, Figs. 7, 8; Plate 17, Figs. 1-5, 13. 



Diagnosis. Sponge body an erect lamella, not simple, but a complex composite of erect 

 lobes, many of which are flattened. Lobes intimately connected below, becoming more 

 free and projecting above. Conuli, 3-6 mm. high on the upper portions and projecting 

 edges of the lobes, nearly absent elsewhere. Dermal membrane finely reticulate to the 

 eye. Color yellowish-gray. Sponge very compressible and flexible, yet firm and elastic. 



Oscula, 2-4 mm. in diameter, over the upper ends and projecting edges of the lobes. 



Oxea very commonly 85-90 /a x 3-4 /*, although larger (100 /«, x 5 /x) and smaller (60-85 /i 



X 2 /u.) forms are abundant. Skeletal bundles 0.5 to 1.0 mm. thick, formed of closely 



interlacing spiculo-fibres, ascend more or less vertically through the sponge body and give 

 off oblique branches which terminate as axial bundles in the conuli. Skeletal network 

 extending between the vertical bundles, on the whole irregular, although fibres directed 

 more or less radially to the surface are everywhere distinguishable. Eadial fibres in parts 

 of the body, invariably in the conuli, extensively developed ; in such places, forming with 

 the approximately transverse connectives a fairly regular skeleton. Stronger fibres of 

 reticulum, 50-80 /n ; connectives, 15-30 /x thick ; ultimate meshes often about 300 /i wide. 

 Larger fibres well filled with spicules ; spongin nevertheless forming a distinct sheath 

 round the fibre. Spongin relatively more abundant in the connectives ; spicules here 



forming from 1 to about 6 rows. Dermal reticulum composed of fibres 40-60 /n thick, 



forming meshes ,subdivided by fibres 15-30 /u, thick ; ultimate meshes, 150-350 /i in 

 diameter ; fibres like those of main skeleton. Abundant villi commonly about 120 yu, high, 

 made up of spicules and spongin, project from dermal reticulum. 



Station recorded as " Acapulco," one specimen. 



The sponge body is essentially an erect lamella, which is, however, 

 curved so that the two ends of the lamella, shown at the right in Fig. 8, 

 Plate 16, are brought close together. Possibly the entire lamella in the 

 natural state encircled some slender upright object. The lamella is by no 



