2 l6 



covered with mud, I think it is easily possible to overlook them : the species is perhaps more 

 common than we suppose at present. In 1908, I received from Dr. van Kampen, who was 

 at that time in Batavia, specimens of the same species, dredged at a depth of ± 45 m. in 

 the Malay Archipelago: Lat. 6°i5'S. and Long. iio°5o'E. 



19. Ba/anus quiiiqitcvittatus n. sp. PI. XXII, fig. 3 — 10. 



Shell conical, greyish-white, having five brownish spots on the rostrum, the latera and 

 the carino-latera, and six small apertures immediately above the basis and between the sutures of 

 the compartments. Scutum with the lines of growth smooth, tergum with the apex not produced. 



This interesting form in certain respects approaches the genus Acasta ; it belongs, no 

 doubt, to the same group of species as B. quadrivittatus ', B. tereöratus, and several other species. 

 It was found attached to the shell of a Gastropodous mollusc. 



The general shape is conical (PI. XXII, fig. 3), with the compartments smooth, not 

 folded or ribbed. The orifice is pentagonal, small, hardly toothed. The carino-lateral compart- 

 ments are narrow. The radii are very narrow and have oblique summits. The colour of the 

 shell is dirty white and is not covered by a membrane. Near the orifice, all the compart- 

 ments, the carina excepted, show a brownish spot, the colour of which corresponds with the 

 bands observed in B. quadrivittatus. The basal margin of the different compartments is 

 irregularly toothed ; in the lower half the compartments are separated from each other by 

 apertures of a longitudinal shape, about the same distance being occupied in the upper half 

 by the radii. This gives the whole of the shell a very peculiar appearance and resembles, 

 more or less, what is seen in Acasta fenestrata. The basis is thin, calcareous, and has no 

 pores, so far as I could make out. The longest diameter of the basis measures 5.2 mm. in 

 the largest specimen, slightly over 4 mm. in a smaller one. 



The scutum (PI. XXII, fig. 4, a and c) has the lines of growth only feebly indicated. 

 It has the basi-tergal angle rounded, no adductor ridge, and the articular ridge narrow, not 

 prominent. 



The tergum (PI. XXII, fig. 4, b and d) has the spur broad, bluntly pointed at the 

 extremity. The basal margin is slightly hollowed out, the scutal margin straight, the apex 

 pointed without being produced. The anterior margin of the spur makes an angle with the 

 extremity of the basi-scutal margin. 



With regard to the structure of the animal's body the following is to be noted: 



Mouth. Labrum (PI. XXII, fig. 5): notch deep and narrow, entrance only slightly 

 wider. Lateral parts, on each side of notch, have an arched or curved outline. Three very small 

 indistinct teeth are disposed between extremely short hairs on each side of notch. Shape of the 

 thickened chitinous portion, which in other species of Balanus is sub-triangular, rhombiform : 

 height and breadth nearly equal. 



Palpi: of peculiar shape, with the upper margin straight and the lower margin convex, 

 the two margins meeting in a rounded-off angle. The whole palpus rather narrow. Shorter hairs 

 are disposed along upper margin, longer ones irregularly scattered over distal half of outer 



