THE SESSILE BARNACLES. 23 



ones on the rostrum. The straight hinge margin is simph^ and the 

 beaks are not produced. 



TSvo specimens measure: Carmorostral length of base 8.5, length 

 between apices 6.3 mm.; diameter of base 7.3 mm.; height of fixed 

 tergum 5.5 mm. C.-R. length of base 14 mm.; between apices 11.2 

 mm. ; diameter of base S, height of fixed tergum 8 mm. 



Internal organs not examined. The specimens were preserved dry. 



This species is strongly individualized by its inornate exterior, the 

 apices of the plates not projectmg, by the very broadly inllexcd basal 

 margins of the wall and by the peculiar, depending adductor ridge or 

 myophore of the fixed scutum. 



Four comjjlcte mdividuals and three more or less imperfect ones 

 were preserved, all being dry. Two are seated on the strong, solid 

 branches of a white coral, the others detached. In four of them 

 the carinorostral length scarcely exceeds the other diameter of the 

 base, the others bemg longer than wide. There is also considerable 

 variation in the degree of development of the external sculpture of the 

 walls as sho"v\Ti in the figm-es, the longer, more strongly sculptured 

 individuals having the parietcs of the fixed scutum and tergum dis- 

 tinctly raised, while in the shorter, smoother form the areas of these 

 plates are nearly even. The myophore and inflexed basal walls are 

 similar in all of the examples. 



Figures 1, 2, 4 are drawn to one scale and represent adult barnacles. 

 Figures 2 and 4 are examples wliich lack the movable plates. Figure 

 3 represents the interior of the fixed tergum and scutum; figure 5 

 the interior of the movable tergum and scutum. 



Section B: VERRUCA. 



Top flattened, the plane of the movable plates not far from parallel 



with that of the base; radio-alar area between parietes of fixed 



scutum and tergum small or linear. 



Type. — V. stromia. 



Group of V. stuomia. 



Much depressed; basal edges of the spreading wall-plates thin and 

 sharp; adductor ridge or myophore well developed; apex of the 

 rostnun marginal. Rami of first pair of cirri subcqual, those of the 

 second and third paii"s very miequal, the thhd pahs bomg like the 

 second, and unhke the fom-th to sixth. Ternunal appendages very 

 long. ShaUow-water forms. 



Tliis group of shallow-water forms is strongly mdividualized, not 

 only by the depressed form, but especiaUy by the cutI, which are 

 more speciahzod than in other Verrucje. The group comprises 

 V. stromia, V. spengleri, and V. Ixvigafa. The second of these species 

 is not contained in the Museum. 



