l8 BROOKLYN INSTITUTE MUSEUM. SCIENCE BULLETIN 2. 2. 
Radula longer than the animal, slender, with six teeth in each row. 
formula, 3.0.3 or i.i.i.o.i.i.i. The teeth are flatly compressed, pointed, 
scarcely curved, destitute of serrations or accessory cusps. The first pair 
or centrals, are tall, narrow, round-pointed, erect or slightly recurved, 
close together, transverse to the radula, the amber-colored bases not wider 
than the cusps. The second pair, or laterals, are as long as the first, 
nearly twice as wide, and stand oblique to the radula, their inner mar- 
gins in advance of the outer and hut little farther apart than the first 
pair, not curved but directed backwanl. The third pair, or uncini. are 
very small, erect, facing inward. 
Types from the north shore of Long Island, N. Y., in the Museum 
of The Brooklyn Institute of Arts and .Sciences, Accession No. 12656. 
Recorded localities : — DeKay : Zoology of New York, Part V., 
Mollusca, 1843, p. 162. "This shell, which is found along our northern 
coast, is now determined to be identical with the P. testudinalis of 
Europe." Doubtless the coast of Long Island is here intended. 
Smith and Prime: Report on the Mollusca of Long Island, Ann. 
Lye. Nat. Hist., N. Y., IX., 1870. p. 392. "Tcctura testudinalis. Gra\-. 
Glencove (Ferguson). Huntington, Grcenport, Little Gull Island." 
Balch: List of Marine Mollusca of Coldspring Harbor. L. I., Proc. 
Boston Soc. Nat. Hist. XXIX, 1899, p. 140 (No. 7). Acinaca testud'- 
iialis (Miiller). "One shell, empty but fresh." 
Li\ing specimens were found by the author at the north end of 
Centre Island (Coldspring Harbor) 1901 and 1902; in Port Jefferson 
Harbor 1912; at Sands Point (Port Washington) 1913; at Wading 
River 1913. 
This Acmaea differs from the species living on the coasts of Maine 
and Nova Scotia in geographical range, habits, size and form of tlie 
shell, and in the form of the teeth of the radula. 
The radula differs from that of testudinalis as figured by Jackson 
in the Nautilus, XXI. 1907, pi. 2.f. i. the centrals being less curved and 
having smaller bases; the laterals being less curved, not noticeably 
arcuate on the anterior face, and their inner margins in advance of the 
outer margins, thus ^^not^ww'. 
More than twenty radulas from specimens taken at Wading River, 
and ten from Sands Point specimens have been examined. In number 
and position of the teeth all are uniform. The radula from an animal 
whose shell measured 20 mm. in length was 23 mm. long, 0.5 mm. wide 
and had four rows of teeth to the millimeter. The growing, or posterior 
end. contained only square transparent plates. A few rows from the 
end these plates bore transparent filaments, appearing like empty sacs, 
slender in form but about as long as the full-grown teeth, and almost 
as wide at the base. These soon fill with a very dark substance, stand 
erect and transverse to the axis of the radula, the centrals in contact 
almost to the apex, the laterals but slightly separated. At about the 
middle of the radula the teeth become golden yellow edged with ma- 
hogany ;,the small amber bases become covered with a pale yellow callus 
uniting those of each row into one mass on either side of the median 
