207 
Dentalium decemcostatum, Brazier. 
Dentalium decemcostatum, Brazier, Proc. Linn Soc., N.S.W., 
1877, vol. it., p. 55. Type locality—Katow, New Guinea, 8 
fathoms, sandy mud (Chevert Exped.); Pilsbry and Sharp, 
Tryon, Man. Conch., 1897-8, vol. xvii., p. 8; Bossevain, Scapho- 
poda, Siboga Exped., 1906, p. 27. 
Dredged in 15 to 22 fathoms in Gulf St. Vincent, 10 
good; with 10 ribs throughout, with 10 ribs posteriorly, and 
more than 10 anteriorly, 24 good. 
Dentalium francisense, n. sp. Pl. xxyi., tigs. 1 and la. 
Shell moderately solid, narrow, curved, less anteriorly, 
translucent white, with 14 broad, low, round ribs extending 
throughout, separated by distinct linear interspaces. Fine 
transverse microscopic growth lines. Anterior aperture cir- 
cular, margins thin, scarcely scalloped. Posterior end trun- 
cate, aperture small, border -thick, shape oval, elongate 
antero-posteriorly. 
Dimensions. —Length, 28 mm.; diameter—anteriorly, 
3°2 mim.; posteriorly, 16 mm. A much younger individual 
measures 135 mm. in length, 2}4 mm. in its anterior 
diameter, and 8 mm. in its posterior. It is much more curved 
and has a slightly projecting appendical tube. 
Locality.—In 15 to 20 fathoms in Petrel Bay, St. Fran- 
cis Island, type with 4 others (2 alive); in 35 fathoms off 
St. Francis Island, 1 good; in 15 to 22 fathoms in Gulf St. 
Vincent, 9 good; in 55 fathoms north-west of Cape Borda, 
1 good; in 15 fathoms in Geographe Bay, Western Australia, 
1 good. 
This shell varies. There may be only 11 ribs through- 
out, of which I have two examples from Gulf St. Vincent, or 
11 ribs posteriorly, and more anteriorly up to 22 from inter- 
calated riblets, 13 examples from the same locality. 
There may be 12 ribs posteriorly and 12 anteriorly, and 
these may he typically broad and round, or rather narrow 
and flat, 4 examples; or of intermediate width, 9 examples; 
or 12 ribs posteriorly and 2 or more additional riblets 
anteriorly, 4 examples, all dredged in 15 to 22 fathoms in 
Gulf St: Vincent. 
There may be 13 ribs throughout, as in 11 examples from 
15 to 22 fathoms in Gulf St. Vincent. 
There may be 15 ribs throughout, as in 9 examples from 
15 to 22 fathoms in Gulf St. Vincent. 
There may be 18 ribs throughout, as in 1 example from 
Port Lincoln, but this is a large old individual, with a rela- 
tively great posterior diameter, and probably had fewer ribs 
earlier in life. 
