ACADEMY OF NATURAL SCIENCES. 295 



tenui expanso in parictem interno, dente lamellari valido iu piano parietis ex- 

 terni expanso, dimidium latitudinis aperturae transeunte ; intervallis dentium 

 parietumque oqualibus. 



Specific Characters. — Shell like a Lacuna, obliquely ovate, the lateral outline 

 subrhomboid. translucent, amber-brown, the spire'produced, apex obtuse, whorls 

 4:%, the third swollen, with four shallow grooves, the posterior one only much 

 impressed, but vanishing on the last whorl ; body with irregular lines of growth 

 undulating across the groove ; numerous scattered impressed points ; aperture 

 ovate, the outer lip acute, purplish, with a double callus within slightly tuber- 

 culate at the middle ; columellar lip white, callous, expanded in the plane of 

 the aperture ; its inner margin subvertical, with two subacute teeth, the upper 

 largest ; a thin callus expanded over the inner wall, with a strong If.mellar 

 tooth expanded in the plane of the outer wall, and crossing half the width of 

 the aperture ; intervals between the teeth and walls equal. 



Long. 0.32 unc.=8 mill. | Long, apert. 0.25 unc. 

 Lat. 0.22 " | Lat. " 0.19 unc. 



Long, spira: 0.1 2=3 " j Div. 40° and 45°. 



Hub. — San Pedro, Cal., estuaries. 



Only four specimens were found dead near the old landing, close to the mouth 

 of the bay, in October, 1861. I supposed them to be P. Urata Binn, but they 

 are nearly three times as large, not 1 irate, etc. That species is catalogued by 

 Carpenter as among the collections from San Diego, in the Supp. Rep. etc., 

 1863, pp. 612, 647, 673, but I do not find it in the State collection. Those de- 

 scribed are fresh and shining in the mouth — dull, but- not much worn, outside. 



This is a very interesting shell, being one of the links between the land and 

 marine mollusca — the species of the genus being chiefly tropical, occurring at 

 Cape St. Lucas, Panama, West Indies, Africa, and Isle of France, according fco 

 Binney, who says that they inhabit crevices of rocks, especially ihose exposed 

 to the full force of the tide ; but being pulraonate, they can probably live long 

 with but little moisture. On the rocks the living shell would be mistaken for 

 a Lacuna or Littorina, and the form of our species reminds one strongly of 

 Succinea Ore<20nensis. 



A communication was received from Dr. Canfield of Monterey, 

 giving an account of the discovery in Monterey Bay, of a fish, pro- 

 nounced by the naturalists of the Smithsonian Institution to be a 

 new species of Bdello stoma, a genus not previously known to exist 

 nearer than the coast of Chili. 



Mr. Falkenau made some remarks on the use and value of the 

 spectroscope in chemical analysis and in other scientific investiga- 

 tions. 



