OBSERVATIONS ON LIVING SOLENOMYA. 27 1 



the periosteum is light yellowish, growing darker as age advances. 

 The hypobranchial gland appears as a mass of globular cells con- 

 taining short rod-like bodies. A number of graceful attitudes are 

 shown in the movements of the pedal disk which I found difficult 

 to figure. The fimbriated edge shows as distinct short tentacles 

 w th grooves running down outside, corresponding to the ten- 

 tacles and corresponding lines or grooves in the disk running to 

 the median line resembling a diminutive actinoid coral Fungia. 

 At other times the edge of the disk appears serrated. These 

 number thirty in all (Fig. n). In the young these resemble 

 long papillae. 



FIG. ii. FIG. 12. 



FIG. ii. Dorsal view of pedal disk. 

 FIG. 12. Side view of foot, showing palp-appendage and branchia. 



The gills are most peculiar in Solenomya. As Pelseneer has 

 shown, there is only one gill on each side having an upward and 

 downward series from a central base. This line dividing the 

 upper and lower series runs from the dorsal anterior portion of 

 the gills to nearly a ventral point posteriorly (Fig. 12). The 

 filaments are distinctly separate and are beautiful in their 

 regularity. The filaments are arranged on the support from 

 which they spring directly opposite each other. Each filament 

 is supported by a chitinous rod in one series, slightly bent at 

 the end firm yet elastic. The same chitinous framework is 

 seen in the gills of Nucula proximo, and Yoldia limatula, as shown 

 by Mitsukuri, Drew and others. Mitsukuri, 7 in describing the 

 chitinous framework supporting the gills in Nucula proximo,, 

 says: "Whether it is really formed of chitin I do not know, but 

 as previous writers have described the substance as of that 

 nature it will be convenient to use the term ' chitinous support' for 

 the present." The gills are colored a light brownish purple, 

 their posterior terminations are free and lighter colored (Fig. 13). 



