554 PROCEEDINGS OF THE NATIONAL MUSEUM vol.84 



Plate 74 



Distichopora sulcata Pourtales: Specimen from station 2354, off Arrowsmith Bank, 

 Yucatan, lat. 20°59'30" N., long. 86° 23'W., 130 fathoms, natural size. 



Plate 75 



Distichopora gracilis Dana: Type, Mus. Comp. Zool, no. 5507, from Tuamotu 

 Archipelago, U. S. Exploring Expedition, X 5. 



Plate 76 



A comparison of the cyclosystems of five species of Allopora, enlarged approxi- 

 mately 30 times; for each species a surface view and a longitudinal section 

 through gastropore and two dactylopores (d) are given to show form of 

 gastropore and gastrostyle (g) . The dactylotomes (d) are in sagittal section. 



1, 2, Allopora solida (Broch): Cotype. 



3, 4, Allopora norvegica pacifica (Broch): Figure 3 is from one of Dr. Broch's 

 white specimens on which the cyclosystems are usually circular. The 

 gastropore is curved so that the tip of the gastrostyle, in profile, is seen on the 

 right side. Figure 4 is from one of Dr. Broch's rose specimens. In both of 

 these the cyclosystems are larger than in examples from stations 5016 and 

 5017 (see pi. 53, fig. 2). 



5, 6, Allopora verrilli Dall: 5, Specimen from Sucia Islands, Wash.; 6, from sta- 

 tion 4777. 



7, 8, Allopora scabiosa (Broch) : Cotype. Figure 7 represents a large cyclosystem 

 with a bent or curved gastropore, the sides of which are as steep as in figure 8. 

 The ventral portion of the gastropore surrounding the style, which might 

 reasonably be interpreted as a style chamber (cf. p. 515), is often not so 

 sharply diff^erentiated from the portion above. In such cases the gastropore 

 is wider opposite the tip of style. In the engraving the roughness of the 

 style-chamber wall is much overemphasized. 



9-11, Allopora boreopacifica (Broch): Okhotsk Sea form, station 5016. Figure 9 

 is one of the larger systems. The smallest are about half this diameter, and 

 may have one, two, or three dactylotomes only. 



U. S. GOVERNMENT PRINTINS OFFICE: t(9t 



