90 UNITED STATES NATIONAL MUSEUM BULLETIN 296 



striations; and the statement of Darwin that C. minutus has "fine, 

 transverse, toothed scales," although he does not picture them. 



Berndt (1907a) does not differentiate clearly between his C minutus 

 striatus subspecies, and Darwin's original C minutus. Apparently the 

 only recourse is to consider them the same species and, in view of the 

 lack of adequate differentiation of a subspecies, to consider the sub- 

 species not properly defined and hence synonymous. 



The variability of the apertural armament is shown in figure 2, 

 with five specimens represented. This variability can cause much 

 concern over the identification of species. The mouthparts and a 

 detailed sketch of the extremely delicate mandible can be seen in 

 figure 3. The segment count for the three terminal cirri in one specimen 

 is as follows: 



Terminal 



cirrus: 12 3 



Ramus: Anterior Posterior Anterior Posterior Anterior Posterior 

 Segments: 15 17 23 25 23 25 



Other descriptive characteristics are well described by Darwin. 



Cryptophialus heterodontus, new species 



FiGUBE 22 



Diagnosis: Cryptophialus with one pair of very reduced mouth 

 cirri and three pairs of terminal cirri; two dorsal body appendages; 

 lateral bars wide and thickened on one edge, pointed, with three 

 single teeth at the posterior end; head reduced; mantle aperture 

 equipped with a series of ranked teeth. 



Etymology: hetero-(GT.) different + odont-{GT.) tooth, for the 

 different tooth sizes on the operculum. 



Distribution: Size of type 1.9 X 0.78 mm, with aperture of 0.24 

 mm, in Tridacna maxima Roding, Heron Island, Queensland, Aus- 

 tralia. Average size of three other specimens: 1.73 X 0.87 mm. Twelve 

 specimens examined. One Turbo sp. from Heron Island had eight 

 specimens of C. heterodontus, 10 specimens of a new species of Crypto- 

 phialus (see p. 107), and two Weltneria reticulata. Three specimens 

 also were found in Distichopora nitida Verr. from the Marshall Islands, 

 R. J. Ethridge, collector, Australian Museum G6234. 



Type-material: Holotype: USNM 122618. Paratypes: Aust, 

 SFSC, Vict. Additional material: BPB, Brit, CA, Paris, Seto. 



The mantle is equipped mth two prominent lateral bars, which are 

 significantly heavier on the dorsal side, giving it a doubled appearance. 

 The posterior end of the lateral bar is near several teeth which are not 

 very prominent. A row of bifid teeth are arrayed on the external 



