482 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.46. 



of Lasiocrinus the possible affinities of the forms hitherto called 

 Homocrinus will be treated at length. Inasmuch as this genus is 

 composed of forms that are so well known, and the characters upon 

 which it is founded are those upon which the genus "Homocrinus" 

 has hitherto been maintained, it is scarcely necessary to describe the 

 genus in any considerable detail. 



LASIOCRINUS, new genus. 



1852. ? Homocrinus Hall part, Paleontology of New York, vol. 2, p. 185. 



1859. Homocrinus Hall, Paleontology of New York, vol. 3, p. 102. 



1879 and 1886. Homocrinus Hall part, Wachsmuth and Springer, Revision of 



the Palseocrinoidea (Author's Edition), pt. 1, p. 77; pt. 3, p. 220, 

 1893. Homocrinus Hall part, Bather, Crinoidea of Gotland, p. 101. 



I B B 5, pentagonal, equal. B B 5, hexagonal, with the excep- 

 tion of post. B and r. post. B which are heptagonal. R R relatively 

 small with the arm facets occupying practically the entire width of 

 the upper faces of the plates. R A rhomboidal, small, resting below 

 on the left shoulder of r. post. B and the right shoulder of post. B. 

 Above it supports x and r. post. R. Anal x rests below on post. 

 B and R A. Laterally it meets 1. and r. post. R R, and above it sup- 

 ports two plates of the anal tube. The anal tube is long and after a 

 point a short distance above its base is composed of a somewhat 

 variable number of parallel rows of small hexagonal plates. The 

 arms are long and in the type species divide by bilateral heterotomy 

 at regular intervals. The arms of earher species are apparently 

 dichotomous, as might be expected. The column is round. In 

 plate 42, figures 10-12 are given to show the essential features of 

 the type species Lasiocrinus scoparius. Figure 10 gives an excel- 

 lent idea of the structure of the ventral sac, and figure 1 1 shows the 

 method of division of the arms and general proportions of the crown. 

 Figure 12 is an analysis of the dorsal cup. The figure of Lasiocrinus 

 tenuis (fig. 9) is given to show the structure of the earlier, Silurian 

 member of the genus. 



Lasiocrinus has a vertical range from the Silurian of Gotland 

 apparently to the Onondaga of New York. Besides the species 

 already noted there are new species probably referable to this genus 

 in the Manlius, New Scotland, Oriskany, Schoharie, and Onondaga 

 formations. The genus is characteristically a Devonian one, with 

 the exception of the Manlius and the Gotland Silurian forms. 



Type of the genus. — Homocrinus scoparius Hall. 



