ICHTHYOCRINIDAE 3OI 



SYNAPTOCRINUS nov. gen 



(auj'a7tT6g, joined; xpirov, lily) 



Plate XXXVIII, figs. 3-6 



Fig. 39. Synaptocrinus 



Ichthvocrinidae with ravs usually in contact all around. Crown elongate, 

 expanding distally from radials up. Infrabasals entirely within the ring of 

 basals. Posterior basal elongate, much larger than others. No radianal. Anals 

 and interbrachials usually wanting. Primibrachs two. Arms dichotomous, in- 

 terlocking, or closely appressed. Column strong, enlarging proximally, cover- 

 ing a large part of the basals. 



Genotype. Forbesiocrinus nuntius Hall. 



Distribution. Devonian ; United States. 



The type of the Devonian species upon which this genus is founded is small and imper- 

 fect, and most of the specimens since found have been of similar character. The discovery 

 of a large and finely-preserved specimen, which has been perfectly cleaned on all sides, dis- 

 closed a well-marked type which could not be referred to any genus heretofore established. 

 It has all the general characters of the family, and superficially bears a strong resemblance 

 to Wachsmuthicrinus, from which the dichotomous arm structure and highly differentiated 

 posterior basal at once distinguish it. 



In all specimens known there is an entire absence of interbrachial or anal plates, the rays 

 being in contact throughout except at the posterior side where they are separated in the lower 

 part by the posterior basal. Considering the disproportionate size of this plate we should 

 expect to find one or more anal plates succeeding it ; but it is doubtful if they occur, for in all 

 specimens thus far observed the posterior basal terminates in a point, fitting accurately 

 between the sloping wings of the first primibrachs, or of the overhanging radials. This is 

 probably a constant generic character, but if as in the case of Wachsmuthicrinus inter- 

 brachials should be found in some specimens, the genus would stand upon its other characters. 

 It is morphologically intermediate between deist ocrimis and Euryocrinns, as it is also in 

 geological position. 



Only the one species is known. 



