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



the exploration of the sea bottom. The number of species known is 

 probably only a fraction of those actually existing. 



The current classification of the species of Scalpelluiu we owe to 

 Dr. Hoek, who composed this scheme of the major groups: 



A. Valves imperfectly calcified. 



B. Valves perfectly calcified. 



A. A portion of the carina projecting freely. 



B. Carina angularly bent. 



C. Carina simply bowed. 



A. AVith a subcarina. 



B. Without a subcarina. 



a. Species with a rostrum. 

 h. Species without a rostrum. 



While this grouping and its amplification in Hoek's key to the 

 species and in Gruvel's later monograph has been of enormous assist- 

 ance to subsequent students, yet it often fails to show the true 

 relationships of man}^ of the species now known, owing to the 

 fact that t?ie shape of the carina and the presence or absence of a 

 rostrum are characters in which there is diversity among very closely 

 related species. I need only instance S. stroemii and its immediate 

 allies, forms no doubt closeh^ akin, yet distributed into two of Hoek's 

 divisions by the characters of the carina; and the species related to 

 S. velutinum^ some of which have a small rostrum, others none. 

 Whether a more natural key will also prove more convenient in prac- 

 tical use than one employing artificial characters remains to be tested. 

 An attempt is made below^ to indicate the natural groups within the 

 genus, so far as I c^n determine them by the material before me. 

 The data existing on the complemental males supports the new classi- 

 fication proposed. 



KEY TO SUBGENERA AND SECTIONS OF THE GENUS SCALPELLUM. 



a. Female and hermaphrodite with a subcarina; male with a distinct capitulum and 

 peduncle. 



h. Only the tergum interposed between the scutum and carina; capitulum 

 Pollicipes-W'k.e] male with the capitulum protected by 6 well-developed 



plates I. Subgenus Calantica, p. 8. 



bb. An upper lateral plate interposed below the tergum, between scutum and 

 carina; capitulum resembling that of normal Scalpellum in general shape. 



II. Subgenus Smiliuin, p. 13. 



aa. No subcarina present; upper lateral plate occupying the middle of the side of 



the capitulum ; male oblong, not divided into capitulum and peduncle, with 



minute valves or none Subgenus Scalpelluin. 



b. Plates well calcified, none of them V-shaped. 



c. Inframedian latus large, subquadrate, pentagonal or rounded-oval, wide 

 in the upper part, the umbo not above the middle. 



III. Section Scalpellum, s. xtr., p. 13. 



