NO. 1 SOOT-RYEN : THE FAMILY MYTILIDAE 87 



support for the anterior adductor separate this group from the typical 

 species of the genus Dacrydiu?n. Hedley's (1906) other species, Dac- 

 rydiuin pelseneeri from New Zealand, seems not to have the grooved 

 teeth but is otherwise very like fabale. Without knowing the anatomy 

 of the species referred to Quendreda, it is impossible to decide if it should 

 be considered as a subgenus or a synonym of Dacrydium. 



Dacrydium (Quendreda) elegantulum new species 



Plate 8, fig. 41 



Diagnosis: Shell small, hyaline with opaque white spots when fresh, or 

 opaque white when dead and worn, oval, with the umbones anterior. An- 

 terior margin with a broadly curved anteroventral angle, ventral margin 

 straight, posterior and dorsal margins evenly curved. Umbones small, 

 pointed. Periostracum thin, shining, growth lines widely spaced and like 

 fine concentric sculpture, slightly raised anteroventrally ; thicker cal- 

 careous layers forming radiating irregular bands on the younger parts of 

 the valve, visible also in full grown and dead shells. 



Hinge with small, toothlike thickenings of the margins on both sides 

 of the deep-set resilifer beyond the umbo, the ventral "tooth" with three 

 or four, the dorsal with five or six, striae or crenulations, the narrow mar- 

 gin connecting them also finely striated across. Along the dorsal margin 

 the anterior part thickened and distinctly striated across, supporting a 

 weak but distinct deep-set ligament. Muscular scars indistinct, anterior 

 adductor placed close to the anteroventral margin. 

 Holotype: The Allan Hancock Foundation. One right valve of a young 



specimen, length, 2.4 mm; height, 1.4 mm. 

 Type loc: Bahia de Gardner, Galapagos Islands (BS 453, Jan. 31, 



1934) ; 35 fms. 

 Remarks: Compared to the Australian Dacrydium fabale, this species is 

 easily recognized by its outline and the opaque radiating spots, as D. 

 {Quendreda) fabale has a concave ventral margin and, as far as known, 

 a uniform consistency of the shell. Most of the material at hand consists 

 of loose valves more or less bored by minute organisms. Two complete 

 but dried specimens were taken in the Galapagos Islands, as was also 

 the fresh valve used as the holotype. The largest valve has a length of 

 4.5 mm. 



Occurrence: Empty valves were taken in depths from 25 to 110 fms. 

 The two living specimens and the type lot were from 25 to 35 fms, 

 where the bottom consisted of rocks or coarse sand. 



Distribution: Galapagos Islands; Baja California north to off Redondo 

 Beach, California. 



