338 LOWER INVERTEBRATES. 



Sub-Order IV. — T^nioglossa. 



The T£Bnioglossate Mollusea are largely marine, though one or two families are 

 found in fresh water. Tlie shell is sjjiral, though in a few forms this apjjearance is 

 obscured. The lingual ribbon in most forms has the shape of a band, and is armed 

 with seven teeth in a transverse row, though in a few forms here admitted there are 

 nine, while in others the number is reduced to three, and occasionally all are absent. 

 Two tentacles are always present. In some the aperture is entire, and in others it is 

 notched or produced into a canal for the respiratory sijthon. We will first consider 

 the holostomate (entire mouthed) forms. 



Our first family contains the periwinkles, the Littoeinid^ of scientific nomencla- 

 ture. This latter name is very appropriate, for they are all shore-living forms. The 

 shell is ovate, with a short, sharp spire, and a round mouth which is closed, on the 

 retreat of the animal, by a horny operculum. They have a tliick foot, large snout, 

 and the eyes are placed at the base of the antennae. They live on the 

 shore between tide marks and feed upon the smaller algte. The principal 

 genus is LUtorina. The first species which we will mention is the peri- 

 winkle proper, L. litorea, the mollusc that is eaten after being extracted 

 from its shell by a bent pin. Our figure represents the species (which 

 is one of the largest of the genus) natural size. The shell is solid and 

 in'autorea'-peti- Very variable in color. Some are banded and some a uniform tint of red, 

 ■winkle. brown, or black, the darker colors predominating. The advance of this 



species on our shores is very remarkable. It is a native of Europe and was first noticed 

 at Halifax several years ago. In 1870 it had appeared on the coast of Maine. In 1872 

 it had reached Massachusetts, but it did not appear south of Cape Cod until a year or 

 two later. Now on both the northern and the southern shores of New 

 England it is one of the most common molluscs. In England it is ex- 

 tensively used as food, the annual catch amounting to many hundreds 

 of tons. It is prepared by boiling, then the operculum is pulled off aiid 

 the meat extracted from the shell. In taste it is much .like the clam, 

 only far more delicate. Though very abundant it has not yet acquii'ed 

 any economic importance here, as the American people seem greatly averse to trying 

 experiments in the gastronomic line. Were it better known, it would be appreciated. 

 Another species which is common to both continents, L. rudis, has received nearly 

 twenty specific names on account of its variations and its extensive range. The gen- 

 eral appearance of the shell may be seen from our figure, but the color is variable. 

 Usually it is yellow or olive-green, and without markings, but occasion- 

 ally specimens are found banded or blotched with some lighter color. 

 Until the advent of L. litorea, LUtorina palliata was the most abundant 

 species on the New England coast. The shell may be either plain or 

 ^toAimpaUMa. variously ornamented with bands and blotches of color, — white, green, 

 or brown. It is common on rocky shores, and is especially fond of creep- 

 ing over the rock-weed {Fuctts) or eel-gi-ass {Zostera). Fui-ther south the common spe- 

 cies is L. irrorata, which is a little larger than L. litorea, but is longer and has a more 

 acute spire. It is comjiaratively rare in southern New England, its metropolis being 

 further south. Its introduction into the waters of Long Island Sound may have been 

 with oysters transjjlanted from the Chesapeake. 



