THE BARNACLES IN THE U. S. NATIONAL MUSEUM. 47 



Section V. 



Rostral latiis high with ahort hanal harder, Visually larger than the 

 narrow inframedlan latas; rostrum narrow or loa^iting; imibo of the 

 carina apical or suhajpical,' carlnal latus higher than vjide, the nmho 

 7wt projecting; plates 13 or llf,. 



A numerous group of small, deep- water species, evidently related 

 to Holoscalpellunu The complemental males so far as known are like 

 those of Iloloscalpellum. 



KEY TO SPECIES. 



«. Inframediau latus wineglass- or hourglass-shaped, being dilated toward the two 

 ends, more or less contracted at or below the middle; the umbo at or below 

 the middle. 

 h. Upper portion of inframedian latus much more expanded than the lower, 

 c. Lower margin of the upper latus straight; no rostrum. 

 d. Plates sculptured with widely-spaced low riblets parallel to lines of growth. 



growth. California _ . - ,S'. lyroximmn. 



dd. Plates with sculpture of unequal growth-wrinkles, and fine, low radial 



stria;. Antilles, etc S. idiopkix. 



cc. Lower margin of the upper latus concave or sinuate; plates marked with 

 weak, spaced growth-wrinkles only; umbo of inframedian latus median; 

 a minute, rounded rostrum between the apices of the rostral latera. Atlan- 

 tic S. sinuatum. 



bb. Upper i)ortion of the rather narrow inframedian latus not much wider than 

 the basal portion, 

 c. Roof of the carina strongly convex, the umbo apical. Atlantic. 



8. gracilius. 

 cc. Roof of carina flat or nearly so. 



d. Umbo of carina removed a short distance from the apex; Atlantic. 



S. carinatum. 

 dd. Umbo of carina apical. 

 e. Carina angular at the sides of the slightly convex roof, the sides»narrow; 

 • umbo of upper latus not entering a bay in the scutum. Southern Cali- 

 fornia S. perlongum. 



ee. Carina with slight ribs at the sides of the flat roof, the sides wide in the 

 upper part; umbo of upper latus entering a bay in the scutum. Atlantic. 



S. cdbatrosifiamnii. 

 aa. Inframedian latus narrowly triangular, tapering upward to the acute apical 

 umbo. 

 b. Carina unusually short, with strongly convex roof. 

 c. Carina not extending up beyond middle of the carinal margin of tergum; 

 rostrum vestigeal or wanting; carinal latus rather small, triangular; infra- 

 median latus reduced *S'. pentacrijiaruin. 



cc. Carina t'xtending above middle of terga; rostrum narrow but well developed; 

 carinal latus pentagonal, very large; inframedian latus well developed. 



/S'. iitio'um. 

 bb. Carina long, its roof flattened, often with bordering ribs. 



c. Plates of the upper whorl with strong radial sciiljjture. Atlantic. 



.S'. formosum. 

 cr. Plates of the upper whorl without consiticuous radial sculpture; inframedian 

 latus very narrow, 

 t^. Rostrum well developed; occludent margin convex; off Chile *S'. gracUe. 



