38 PEOCEEDINGS OF THE NATIONAL MUSEUM vol.72 



nomenclature because of the small number of recent species known. 

 Moreover and in consequence of this observation, an exact determi- 

 nation of a Crihrilina can be made only after a special preparation of 

 its costular system. The number of specimens of the same species 

 is almost always quite small and it is then often hard to destroy 

 them in order to make the technical preparations; but it is necessary 

 to decide in favor of science, which is becoming more and more exact. 



CRIBEILINA LINEATA, new species 



Plate 3, Figures 5, 6 



Description. — The zoarium encrusts nullipores; it is formed of 

 isolated zooecia, arranged in linear series. The zooecia are large, 

 elliptical, elongated; the frontal is very convex surrounded by a 

 kind of smooth gymnocyst to which the costules are attached; the 

 costules are narrow, adjacent, and separated by very small and linear 

 lacunae; they bear at their extremity a salient lumen pore; they are 

 united on the median axis by a salient thread; they are 16 in number. 

 The aperture is semielHptical, transverse, with concave proximal bor- 

 der; the peristome bears two or three short, broad spines and two 

 lateral tongues which develop and unite together sometimes to form 

 an arch above the aperture. The ovicell is hyperstomial, closed by 

 the operculum; it bears a large longitudinal keel and two lateral 

 circular scars. 



nr ^ * i Ilia = 0.l5 mm. 



Measurements. — Apertureu ^ ^^ 



Ua = 0.25 mm. 



„ . [is =1.00 mm. 

 Zooecia 7 ^ __ 



Us = 0.60 mm. 



Structure. — The opercular valve is very thin, the costules are thin 

 and translucent; they are juxtaposed and separated sometimes by 

 very narrow and linear lacunae ; they bear an apparent lumen line 

 and three or four small lumen pores; finally they are joined at their 

 base and form the false gymnocyst which surrounds each zooecium. 

 This structure is quite identical with that which Norman, 1903, fig- 

 ured for Crihrilina annulata. He did not illustrate the lumen line 

 because, as he wrote, the opaqueness of the costules prevented the 

 view of it, but in the text he affirms its presence as well as that of 

 the lumen pores. It should be noted also that the variety spitzber- 

 gensis of the same species bears as here two lateral tongues to the 

 aperture. 



Biology. — Our specimens were in reproduction April 30, 1884. 

 Each colony contains only a very small number of zooecia. The 

 protective influence of the apertural arch is rather difficult to under- 

 stand: we have observed it only on the ovicelled zooecia; it must 

 retard very much the extrusion of the tentacles. 



