140 SYSTEMATIC ARRANGEMENT 



1. ROTELLA. 



Shell orbicular, depressed, polished; porcellaneous axis callous; 

 mouth circular, with a columnar groove. 



I. R. lineolata, t. 38. f. 7, 8, t. 107- f. 6. 



Littoral, burying themselves in the sand left by the sea at low 

 water. 



Foot of Rotella lineolata truncated in front ; when contracted, in 

 spirits, with a deep central groove, and with the side edges folded 

 down in front ; lateral fringe with three tentacles on each side ; 

 the front one on the right side, near the eye, produced into an 

 oblong fleshy lobe which partly covers the base of the shell, 

 and probably forms the callosity. Tentacles two, subulate ; right 

 larger, free, with an oblong, compressed lobe on its hinder side, 

 with a very indistinct indication of an eye on the inner side of the 

 end ; hence probably a modified eye-pedicel. The left tentacles 

 smaller, partly attached to the upper side of the left eye-pedicel, 

 which is cylindrical, with a large membranaceous expansion attached 

 to the whole length of the side, which is fringed with small beards 

 on the edge, and folded to the right over the mouth towards the 

 right tentacles, and then folded back and continued by a slightly 

 elevated ridge with the front edge of the left lateral fringe. Muzzle 

 none. Mouth circular, sunken, under the base of the curious-shaped 

 veil. Proboscis short, retractile. Lingual membrane elongate, with 

 numerous setaceous teeth suddenly bent ; the innermost series dilated 

 beneath the bend and the end, and finely denticulated near the tip ; 

 denticulated hooks at the tip in oblique series on each side, without 

 any central teeth. 



According to Dr. Loven, the central tooth of Rotella lineolata 

 is longitudinally subrectangular, unarmed ; lateral six on each side, 

 of which four are gradually a little longer, and are almost of the 

 same shape as the central one ; fifth and sixth elongated, keeled, 

 the former linear, bent, the latter subfusiform ; lateral series of teeth 

 nearly equal in size, with an oval hook, in the inner ones denticu- 

 lated behind at the flexure, in the middle one on all sides ; scape 

 arcuate, produced under the hook. 



" Animal of Rotella opake white. Foot large, flexible, edge often 

 playing up against the shell, with a lobe on the side of the mantle 

 partly clinging to the shell, but not enveloping it. Mouth a curious 

 siphon-slit next the outer lip of the shell, and filled with cilia. Ten- 

 tacles four ; one of these, bearing the eyes, forms an edge to the slit ; 

 the other bearing the eyes, and two other tentacles, free their whole 

 length, the latter having roots inside the siphon. Cilia of siphon 

 tipped with black ; sometimes they gather against the sides, so that 

 you see a tube with a black rim, but usually they are rayed. 



" The Rotellce live where they are left dry at least two hours each 

 tide, just buried in the sand ; when placed in water they did not 

 move about much, only raised up their siphons, so I conclude that 

 they feed on the minute living things brought to them by the water." 

 — Fairbank, Ann. Lye. N. York, 1853, p. 35. 



