Calvin on a new Tubicolay An-,u\ui. 27 
anything to snggest generic relationship between these worm 
tubes of Acervularia and the Saltcrella of Billings, (Pal. Fossils,, 
vol. i, p. 17-) This last genus comprises "small, slender, elon- 
gate-conical tubes, consisting of several hollow cones placed one 
within another." The pretty spiral worm tubes of the genus 
Spirorbis are coiled in a plane and attached by one side only. 
The tubes that constitute the subject of this paper differ from all 
others known to me in being more or less regularly coiled around 
an elongated axis, and in being from the beginning of their 
growth supported on all sides. I therefore, provisionlly at least, 
propose to make them the type of a new genus as follows: 
Streplindyles, n. g. Worm solitary, inhabiting a simple cal- 
careous tube sjDirally coiled around an elongated imaginary axis. 
Diameter of tube increasing very gradually from the apex,, 
sometimes constricted between the volutions. Tube walls thin, 
marked externally by parallel lines or annulations of growth. 
Mode of growth apparently requiring that the tube be supported 
equally on all sides. The tvpical species growing vertically in 
corals. 
Streptindytes acervalaricB, n. s. Tubes with the spiral sinis- 
tral, growing in greater or less numbers in coralla of Acervula = 
ria davidsoni. Tubes varying from one-eighth to nearly one 
fourth of an inch in diameter, and from one to two inches in 
length. Surface marked by fine parallel lines of growth. No 
longitudinal stride. Spiral somewhat irregular. In a typical 
example, where the tube is about one eighth of an inch in diame- 
ter, the distance from middle to middle of two contiguous volu- 
tions is one fourth of an inch. 
Found in strata of the Hamilton period, Devonian age, at 
Robert's Ferry, Iow\a. 
Species of Streptindytes may have lived in other corals than 
Acervularia. They may have lived indeed embedded, tip 
downward, in soft mud, or in any other situation where the 
growing tube would be subject to similar conditions on all sides. 
They could never have had the habit of Serpula or SerpuHles, 
the genera to which Streptindyles, in the matter of shell struc- 
ture, stands most closely related. 
Finally it is highly probable that at least specific modification 
was necessary to enable our Robert's Ferry species to establish 
