THE BARNACLES TN THE U. S. NATIONAL MUSEUM. 25 



SCALPELLUM ANGUSTUM Sars. 



Localiti/. — Cat. No. 172()G, LJ.S.N.M. Kara Sea. Dijinphna expe- 

 dition 1882-83. 



Distinct from ^*?. pressani by the terminal umbo of tlie carina, the 

 higher position of the umbo of the carinal lateral plate, and the 

 parallel-sided rostrum. The teroum in these specimens does not 

 project so far upward as in CTruveFs figures. 



Section IV. HOLOSCALPELLUM, new section.. 



Rostral latus wide and low, Its loldth UHu<dly douhle the heigltt^ with 

 long snhparallel hasal and scatal horders; infravLedian latus smaller 

 than the rostral latus; rostrum small or wanting; carina -with the 

 umho apical or near the ape.c; plates 13 or 11^.. Type,, 8. velutinum. 



A large natural gi'oup of almost exclusively deep-sea species, widely 

 distributed in both Atlantic and Pacific waters. Besides the species 

 considered below, the following belong here: S. daranni,, S. gigas^ IS. 

 moluccanum^ S. rubrum, S. antarcticum, S. hirsufum, S. indicum, S. 

 pedunculatum^i S. sociahlU., S. alcochianum, and probaljly some others. 



The compleraental males are sack-like, with no division into capit- 

 ulum and peduncle, and have excessively minute valves or none. 



KEY TO SPECIE.S. 



a. Carinal latus much wider than high; umbo recurved, near the upper margin. 

 Species of large size. 

 b. Plates in contact; carina very broad at base, breadth \ to ^ the length, roof 



flat or concave between raised lateral borders >S'. velutinum. 



hh. Plates separated by wide chitinous sutures. 



c. Carina rounded dorsally; valves covered with a thick cuticle; umbo of carinal 



latus not projecting S. giganteum. 



cc. Carina with flattened roof bounded Ijy angles, and narrow tliroughout; umbo 



of carinal latus projecting laterally S. regina. 



aa. Carinal latus about as high as wide, the umbo apical; inframedian latus wider 

 than high. Large species. 



b. Roof of tlie carina slightly convex, angular at the sides S. regium. 



bb. Roof flat with l)ordering ribs: inframedian latus larger S. regium latidorsum. 



aa. Carinal latus about as high as wide, the umbo projecting directly backward 

 beyond the carina; inframedian latus narrow, hooked forward; umbo of 

 carina at the middle of carinal margin of tergum. Small, violet-tinted. 



S. gorgon ioph ilnin . 

 aaaa. Carinal latus about as high as wide, the umbo recurved, at or below the middle 

 of its carinal border. Small species. 

 b. Inframedian latus narrow and high, oblong or tapering upward, without con- 

 spicuously produced angles. 

 c. Upper end of inframedian latus rather acute. Atlantic. 



d. Capitulum not tapering toward the base; apex of inframedian latus curved 

 toward the scutum. 

 e. Umbo of carinal latus about median on the carinal border. 



S. portoricanum intonstim. 



