or Little Known, Polyzoa. 3T 



specimen the zoarium is almost entirely bilaminate, the lobes 

 being considerably larger, and only a small part encrusting ; 

 however, here also the laminae are in part separated to 

 embrace an annelid tube. 



Diastopora capitata, n. sp. PL II., G.g 2. 



Zoarium consisting of bilaminate lobes, rising from an 

 encrusting layer by a narrow, stem-like portion, and 

 expanding above ; laminee separated b}^ a calcareous 

 septum J slightly produced beyond the zooecia. Zooecia 

 slightly free at the extremities, indistinct, minutely 

 punctate. 



Port Phillip Heads, Mr. J. B. Wilson. 



The only specimen I have seen consists of a cluster of 

 four lobes, rising from an encrusting layer of zooecia. Each 

 lobe is narrowed and thicker below, expanded, thinner, and 

 undulated above, and usually divided into two secondary 

 lobes. The summit of the lobes is flatter than in the last, 

 and cellulai from the opening of imperfectly formed cells. 

 The zooecia are not so numerous on the stem-like portion, 

 but increase in number and prominence upwards, until 

 towards the summit they are considerably elongated to 

 assume a corymbose appearance. In the encrusting part a 

 few of the zooecia are closed, the lid having a minute per- 

 foration in its centre. In both species the dividing septum 

 is not visible on the sides of the lobes, but only on the 

 summits. 



The genus Mesenteripora was proposed by Blainville, and 

 has been adopted by D'Orbigny, Sinitt, Busk, and others 

 for those diastoporidan forms having the zoarium formed of 

 two layers of zooecia, parted by a thin calcareous septum, and 

 opening on both sides. One species {M. meandrina, Series- 

 Wood) has been found recent in Greenland and on the coast 

 of France, as well as fossil in the orag ; and several others 

 have been described from various fossiliferous formations. 

 The two species here described are especially interesting, as 

 being the only other recent forms referable to Mesenteripora, 

 and also as showing that there is no valid distinction 

 between that genus and Diastopora. D. cristata, when 

 enveloping the bundle of annelidan tubes, is a Berenicea ; 

 when encrusting a nodule it is a true Diastopora, and 

 when erect and bilaminate a Mesenteripora. D. capitata. 



