TAXOCRINIDAE 415 



rected by those interested, and all such specimens should be labelled Taxocrinus colletti as 

 explained under that species. 



This species is exceedingly rare, not having been found except at the horizon and in 

 the vicinity mentioned above. 



Type. Worthen collection, University of Illinois. The other specimens herein figured 

 are in the author's collection. 



Horizon and locality. Lower Carboniferous, base of Keokuk limestone; Nashville, 

 Iowa, and Nauvoo, Illinois. 



Parichthyocrinus subovatus (Miller and Gurley) 

 Plates XXI, fig. 6; LX1I, figs. 4-17; LXIII, figs. 1-4 



Taxocrinus subovatus Miller and Gurley, 16th Rep. State Geologist Indiana, 1890, p. 347, pi. 5, fig. 3. 



A medium sized species, very similar to P. meeki; differing mainly in its 

 generally more elongate crown, and more lozenge-shaped interbrachial areas; 

 it is also apparently smaller, as out of 40 specimens the largest is 34 mm. 

 high by 30 mm. wide, and few attain a size of 30 by 25 mm. The average of 

 six representative adult specimens gives the following proportions : height 

 to width of crown at upper IIIBr, 1.1 to 1 ; of calyx at I Ax, 1 to 3.5; spread of 

 calyx from column facet, 1 to 3 ; so the crown is not so wide as that of P. meeki, 

 and the calyx is higher and not so nearly horizontal below. 



These characters of course have the minimum diagnostic value, and seem to be only 

 of importance because they occur quite uniformly in a large number of specimens which 

 are derived from a different horizon, viz., the upper part of the Keokuk limestone. If one 

 of these specimens were found at the Iowa locality and horizon we should scarcely think 

 of separating it from meeki. The difference in the interbrachials seems marked by a ten- 

 dency to double the large plate in the second range, with another large one following in the 

 third, thus making the areas more broadly oval. There is also a slight difference in the 

 column in the rather greater contrast of alternating columnals in this species, although, in 

 both they take on great uniformity in the lower half of the stem. We have the stem com- 

 plete in the two beautiful specimens figured on Plate LXIII, figures 1, 2, both of which show 

 traces of irregular cirri for a considerable distance from the distal end ; the stem tapers to a 

 fine point without branching roots, and in a medium sized specimen is about 8 inches long. 

 The IIBr are fairly constant at 3, a tabulation of the facts in 15 good specimens showing 

 that number in 75 per cent of the rami, and 4 in the others. Right and left posterior radials 

 are usually both reduced in size. 



The fine series of specimens studied were found in two colonies at the Indian Creek, 

 Indiana, beds, but the type and a few others came from the equivalent horizon in Washing- 

 ton County. This is one of the species which may be thought over-illustrated, resulting 

 from the repeated accession of better material as the drawings were in progress, the two 

 complete specimens having been obtained twenty years after the first discoveries at the 

 locality. I have illustrated along with them a specimen with a solid anal series in the lower 

 part, occurring in the large colony of specimens otherwise like it, which if found isolated 

 might readily pass for Euryocrinus (PI. LXIII, figs. 3a, b) ; I consider this only a sporadic 

 occurrence ; and in fact a close examination of the anal series shows traces of its Taxocrinoid 

 affiliation in the presence of small plates at either side and an open space at the top (fig. 3c). 

 There are one or two others with plates in similar condition. 



The specimens figured on Plate LXII show a gradation from four large interbrachials 

 in the adult down to one in the young ; the type is an intermediate specimen with two, and 

 was so described by the authors. 



