102 Scientific Proceedings, Royal Dublin Society. 



investment, which is opaque, leathery, flexible, and rough ; the 

 investment breaks off abruptly at each of its extremities, and is 

 more deeply furrowed and wrinkled, and studded with particles of 

 sand at its anterior end. When the animal is much contracted 

 eight longitudinal ridges sometimes rise at the anterior extremity, 

 and extend for a very short way down the scapus : no other longi- 

 tudinal marks are visible except when the animal is much dis- 

 tended, in which case the lines corresponding to the insertions of 

 the mesenteries can be seen through the investment, especially in 

 the region towards the physa. When the investment is removed 

 the insertions of the mesenteries are seen in the body-wall as in 

 Peachia hastata. 



Capitulum — delicate, retractile within the scapus, columnar ; its 

 body-wall is divided perpendicularly into eight broad regions, 

 separated by as many narrow flutings ; the broad regions (which 

 apparently correspond to Grosse's " invections "), being somewhat 

 swollen. 



Tentacles — marginal in two rows, the inner usually pointing 

 upwards, the outer extending horizontally ; obtuse, slender, hardly 

 tapering towards the top. 



aa — tentacles 22 in number, 8 being arranged in the inner row, 

 one at each end and three at each side of the mouth. Each of the 

 inner tentacles thus occupies the centre of one of the inter-mesen- 

 terial chambers. From between the mesenteries which run into 

 either end of the mouth (" the directive mesenteries ") there rises 

 but one tentacle. At one end of the mouth each of the chambers 

 adjoining that formed by the directive mesenteries have four ten- 

 tacles — one in the inner and three in the outer row. Each of the 

 remaining chambers gives rise to three tentacles — one in the inner 

 and two in the outer row. 



/3/3 — tentacles twenty in number, arranged ten in the inner 

 and ten in the outer row. 



Bisk — usually elevated into a cone ; each inter- mesenterial space 

 being arched upwards between the mesenteries, and having a some- 

 what puffed and swollen appearance. 



Mouth — prominent ; linear ; lips frequently protruded and 

 folded back over the disk. 



Colour. — Physa — pellucid white, marked with eight white Ion* 

 gitudinal lines. 



