1886.] NATURAL SCIENCES OF PHILADELPHIA. 143 



The following species have been described : 



1856. Carabocrinus radiatus Billings. Type of the genus, Geol. Surv. Canada, p. 

 276; also 1859, ibid. i>ecaueiv, p. 30, PI. 2, figs. .3 a-c ; also W. and Sp., Re- 

 vision i, p. 144. Trenton limest. Ottawa, Can. 



1859. (?) C. tuberculatus Billings, Geol. Surv. Can., Decade iv, p. 3.3, PI. 10, figs. 

 2 a-c. Hudson River.gr. Island ofAnticosti. 



1859. C. Van Courtlandti Billings, Geol. Surv. Can., Decade iv, p. 32, PI. 2, fig. 4. 

 Trenton limest. Township of McNab, Can. 



EUSPIROCRINUS Angl., Rev. I, p. 143. 

 AMPHERISTOCRINUS Hall. 

 1882, 11th Geol. Rep. Indiana of 1881 by Collett, p. 278. 



This is one of the few genera of the Cyatliocrinidae which have 

 only three underbasals, and this distinguishes it readily from 

 Homocriniis , with which it agrees in the plates of the azygous 

 side. 



Generic Diagnosis. Underbasals three, two equal and with 

 truncate upper sides ; the third one-half smaller, angular above. 

 Basals five ; two of them resting entirely upon the two large 

 underbasals ; pentagonal ; the two alternating with them hexa- 

 gonal ; the posterior one, which has a truncate upper side, hep- 

 tagonal. The latter is larger and supports toward the right a 

 pentangular azygous plate ; at its truncate upper side a large anal 

 piece ; along the left side a radial. The azygous plate is followed 

 b}^ the anal plate, which is laterally connected with the right pos- 

 terior radial. The radials are pentagonal, with a small semi- 

 circular excavation for the reception of the arms. Onl}' one 

 brachial is known, which is quadrangular and extremely small. 

 All other parts are unknown. 



The only known species is : 



1882. Ampheristociinus typus Hall, Uth Ann. Geol. Rep. Indiana by Collett, p. 

 278, PI. 15, figs. 17-18. Niagara gr. AValdron, Indiana. 



DENDROCRINUS Hall, Rev. I, p. 75. 



The following species must be added to our list : 



*1856. Dendrocrinus angulatus (Billings), Palaeocrinus angulatus, Geol. Surv. 

 Canada, p. 269: also Decade IV, PI. 3, figs. 6 A. Cyathocrinus angu- 

 latus, Rev. I, p. 85. Trenton limestone. Ottawa, Canada. In examining 

 the tvpe-speciuien in the Canada Survey Museum, we found it to be a good 

 Dendrocrinus. Toward the right of the basals, underneath the postero- 

 lateral radial, it has a good-sized azygous plate, which at its left sloping 

 upper side supports an anal piece, exactly as in Dendrocrinus. The s[iecieg 

 has a strong ventral tube, of which only the transverse section is seen, 



