36 PROCEEDINGS OF THE NATIONAL MUSEUM vol.76 



peristome presents traces of spines. Our specimens were living and 

 ovicelled April 9, 1888. 



Occu7^rence. — Galapagos Islands, D. 2815. 



Holotype.—C'At. No. 8508, U.S.N.M. 



LAGENIPORA MAEGINATA, new species 

 Plate 6, Figures 2-3 



Description. — The zoarium incnists shells and often dead Cupu- 

 laria umhellata; it is formed of large linear branches, generally tri- 

 serial, sometimes spreading out palm shaped. The zooecia are dis- 

 tinct, margined by a salient thread, much elongated; the frontal is a 

 tremocyst with very small pores separated by very fine granules, 

 superposed on the olocyst; it is convex and supports laterally two 

 small orbicular avicularia. The peristomie is short, very oblique, 

 costulated; the peristome is orbicular and irregularly denticulated. 

 On the long peristomies the peristome is widened and adorned with 

 denticles and very irregular spicules. The ovicell is very small, 

 always fixed at the base of the peristomie, and ornamented with a 

 small, finely perforated area. The ancestrula is a small ordinary 

 zooecium. 



Measurements. — 



[Zs= 0.60-0.7 mm. |7ia= 0.12 mm. 



Zooecium I ^^_Q 30 j^j^ Aperturaj ^^_q 10 j^^^^ 



Variatiojis. — Uni or biserial branches are not rare. The colony 

 is most often fixed on very small objects. The movements of the 

 latter do not bother it. It develops on occasions on both sides of the 

 substratum, and we have seen it even on the edge of the small shell 

 fragments. 



The peristomie is generally short; it is much elongated accord- 

 ing to rule in the sheltered or narrowed parts of the substratum. 

 The peristome then enlarges considerabl}^ and presents the most 

 fantastic cut edges. 



A-ffi/nities. — This species differs from Lagenipora spinulosa Hincks 

 in its much greater dimensions, in its more numerous pores, its 

 shorter periostomie, and the presence of small frontal avicularia. 



Biology. — Most of our specimens were living, and many of them 

 were ovicelled April 7, 1888. 



The habits of Lagenipora resemble very much those of Prohoscina 

 which in the Cyclostomata have the same zoarial arrangement. 



Occwrrence. — Galapagos Islands, D. 2813. 



Gotypes.—Cmi. No. 8510, U.S.N.M. 



