1 is THE VOYAGE OF H.M.S. CHALLENGER. 



beaked. Spur placed in the middle of the basal margin. The basal margin, on opposite 

 sides of the spur, does not form a nearly straight line, the soutal portion is about at 

 right angles with the spur: the carinal portion descends nearly as low as the scutal half, 

 but it is hollowed out in the middle, and describes with the spur an angle less than a 

 right angle. The spur is relatively stout ; its breadth is exactly one-fourth of the breadth 

 of the valve. The scutal margin is very broadly inflected, the inflected portion forms 

 less than a right angle with the interior surface of the valve. The articular ridge is very 

 prominent and nearly straight ; it extends about half-way down the valve. The spur is 

 produced for a considerable distance up the internal surface of the valve as a prominence. 

 The crests for the tergal depressor muscle are well developed. The scuta and terga 

 were calcified together; but they readily became loose after having been boiled in caustic 

 potash. 



Judging from the form of the scutum, our specimens might be considered either 

 as var. coccopoma, as var. concinnus, or as var. communis. However, var. coccopoma 

 is globulo-conical, with a small rounded orifice, and generally has smooth walls, and 

 this is not the case at all with the specimens under consideration. Var. concinnus 

 is also globulo-conical, and has finely ribbed walls. Its scutum, moreover, shows a cavity, 

 bordered by a plate, for the rostral depressor muscle ; the cavity is present in the scutum 

 of the Challenger specimens as it is in that of every specimen, but the plate is 

 wanting. 



The specimens collected during the cruise of H.M.S. Challenger are from St. Vincent 

 Harbour, Cape Verde Islands. They were taken towards the end of July 1873, at a depth of 

 from 7 to 20 fathoms. The thick calcareous ] ayer that covers both specimens is inhabited 

 by a small Barnacle, belonging to the genuj Chihamalus, and identical with Chiha- 

 malus dentatus, Krauss. 



The other form, which represents Balanus tintinnabulum, Linn., in the Challenger 

 collection, is the variety (G) spinosus (Gmelin). This variety has been figured by Darwin, 

 and by means of this figure, as well as his description, it is very easily distinguished ; 

 it is globulo-conical or cylindrical ; its shell is rather thin, with long, nearly cylindrical, 

 very sharp points directed upwards ; colours very pale. The specimens before me arc 

 rather flat-conical, and they are not pale, but beautifully purple-coloured ; the spines are 

 especially dark. The radii are narrow and pale coloured, with slightly darker transverse 

 lines. The orifices are very small. I tried to prepare the opercula ; but, having boiled 

 them with caustic potash, they became so very brittle as not to allow of a trustworthy 

 inspection. The tergum is distinctly beaked, the spur rather long and placed at about 

 its own width from the basi-scutal angle. The adductor and articular ridges of the 

 scutum were partly broken off — so I cannot judge of them as to their distinctness, &c. 

 The specimens are all very small ; their base is nearly circular, and has in the largest 

 specimen a diameter of about 7 mm. The height of this specimen is not quite 4 mm. 



