MOLLUSGA. CEPHALOPODA. Arethusa. 
depression is observable, and produced by the margin of the last chamber 
rising on the side of the second. The chambers are rounded externally. 
18. V. suhrotundum . — ^Mouth depressed, toothless. 
Serpula subrotunda dorso elevato, Walk. Test. Min. t. i. f. 4.— Ver. sub. 
Mont. Test. Brit. 521, Flem. Wern. Mem. iv. 565. t. xv. f. 5. — Com- 
mon. 
Globular, chambers three, rarely four, inflated and wrinkled. The fourth 
chamber, when present, seems always imperfectly formed. 
19. V. hicorne. — The last formed chamber striated longitudi- 
nally. 
Serpula bicornis ventricosa. Walk. Test. Min. t. i. f. 2 — Ver. bicorne, 
Mont. Test. Brit. 519. — Sandwich and Reculver, Mr Boyes. 
Length one line ; chambers three, the middle one small, raised or depres- 
sed ; the last chamber is suboval, compressed, striated longitudinally on the 
longer side from the aperture ; the other side is smooth : It contracts to- 
wards the mouth, which is very small and orbicular. 
These species belong to the genus Milista of Lamark, Instituted many years 
subsequent to the Vermiculum of Montagu. * The fossil species of France are 
numerous. 
Gen. VII. ARETHUSA.? {of Montfort). — Cells arranged 
obliquely and alternately along an axis, with the mouths 
of all the chambers having an aspect towards the same 
pole ; forming a subturriculated shell. 
20. A. lactea. — Chambers ovate, aperture circular. 
Serpula tenuis ovalis laevis. Walk. Test. Min. t. i. f. 5 — Vermiculum 
lacteum, Mont. Test. Brit. 522. Flem. Wern. Mem. iv. 566. t. xv. 
f. 6. — Among corallines, English and Scotch coasts. 
Length about J^th of an inch, delicately transparent, with the inner walls 
of the chambers appearing as white veins. The chambers are six or seven in 
number, weU defined on one side, obscure on the other, contracted towards 
the mouth. Walker and Montagu obtained this species at Sandwich and 
Devon, Captain Laskey at Dunbar, and I have it from Leith and Zetland. 
Gen. VIII. LAGENULA. — Shell with a globular body, ha- 
ving a produced neck or tube. 
* With longitudinal marhings. 
21. L. Shell pellucid, with opake,fine, longitudinal 
striae. 
Serpula (Lagena) striata sulcata rotundata. Walk. Test. Min. t. 1. f. 6. 
—Vermiculum striatum, Mont, Test. Brit. 523. — Not uncommon in 
sand on the English shores. 
In shape, this species resembles a Florence flask ; rounded retraUy ; the 
mouth is slender jind produced, with a small round aperture ; length not 
half a line. 
