52 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
solitaria; basi ad conchas, seu altera ad alteram, constricte adhaerent e? 
saepe erodente; superficie rugis irregularibus spiralibus baud extantibus, e t 
rugulis increment ornata; intus anfr. promis, et ultimis quoad iv., apertis; 
medianis laminatis; lamina superiore multo majore, prius conspicua, a 
columella extante; primum simplici, dein angulo recto reflexa, extus, 
carinus i-iii. quarum ii. acutissimis; lamina inferiore simplici, a col^. 
mella extante, altero juxta carinam fere attingente; lamina tertia minima, 
intercalate, inferiori paene attingente; laminis tenuissimis, albis, diaph- 
anis, lineis incrementi conspicuis; pagina interna maxime nitente, trans- 
versim haud septato. (Carpenter.) 
The shell is of small diameter; when growing freely taking a tolerably 
regular spiral, like a Turritella squeezed sideways; the whorls enlarging 
very slowly, and resembling a winding staircase. It is known when fresh 
by its lustrous purple-brown color and absence of pits on the surface. It 
occasionally eats into the shell on which it grows, like Spirogly pints, from 
which it is known by being dextral and cylindrical. Sometimes it clusters 
in large masses, like Bivonia glomerata . At which whorl the internal 
laminae commence, it is difficult to say; they have been counted running 
through 10 whorls; and the terminal number of open whorls appears to 
vary. At each end they commence (the large upper one first) as simple 
columellar plaits, afterward increasing till they fill the greater part of the 
cavity and nearly meet. The upper one bends, at right angles, with two 
sharp keels at the corners, and a third, not always developed, on the upper 
side. The lower one goes to meet it, forming with the columella a rec¬ 
tangle, only communicating with the remainder by a narrow slit. A small 
columellar plait supports the inside base of the lower lamina. The delicate 
texture of these laminae resembles the cup in Crucibulum, etc. No trans¬ 
verse partitions have been seen. Long., 65; lat., 13 poll. (Carpenter.) 
Type in Liverpool and Havre collection. Type locality, Mazatlan. 
Range. San Diego, California, to Panama. 
Petaloconchus complicatus Dali, 1908 
Bulletin, Museum of Comparative Zoology, 43:326. 
Coil at first closely wound and more or less obliquely bent in con¬ 
formity with its situs, the first few turns with a subcircular section, very 
irregularly disposed, those following with a roughly hexagonal section 
closely coiled around a barely perforate axis, closely coherent to each 
other and running up to twenty or more in number, after which the tube 
once more becomes erect, with a circular section, and a slight dextral 
[ 654 ] 
