4 PROCEEDINGS OF THE NATIONAL, MUSEUM. vol.61 



EXPLANATION OF PLATE. 



All figures natural size unless otherwise indicated. 



Balanocrinus mexicanus, new species. 



Fig. 1. The type. Part of a large stem fragment 25 cm. long, 12 mm. to 10 mm. 

 in diameter, belonging to a column traced in the rock to a length of 

 5 meters ; it shows 3 complete inteniodes of about 20 columnals each, 

 and a nearly complete cirrus about 15 cm. long, composed of 52 os.sicles 

 and tapering from 4.5 to 2 mm. ; it also shows the origin of 2 opposite 

 cirri from one nodal. The entire fragment from which the figure is 

 made has 4 internodes, and 4 more or less complete cirri preserved. 

 Acq. No. 268. 



2. Stem fragment of about maximum diameter — 17 mm. — showing 2 oppo- 



site cirrus sockets. Acq. No. 135. 



3. Stem fragment containing 2 cirrus-bearing nodal columnals, of which 



the lower one has 2 cirri (one not visible, in this view) and the upper 

 only one, with 16 internodals between them. Acq. No. 142. 



4. Joint-face of same, showing triangular sunken areas of the ligament 



fossae, or petaloid sectors, having about the usual relative propor- 

 tions, with crenelations limited to the peripheral band, about 10 to 

 each sector. X|. 



5. Fragment of larger stem — 15 mm. diameter. Acq. No. 135. 



6. Joint face of same, with crenelation deeply exposed, showing alternate 



grooves rather strong, enclosing intermediate grooves which may some- 

 times be undeveloped, leaving less than 10 apparent in the fossil. X| 



7. Fragment of small stem, 6 mm. diameter, with a single cirrus socket. 



Acq. No. 138. 



8. Joint-face of same. X|. 



All the foregoing from upper part of the San Felipe formation. 



9. Stem-fragment 8 mm. diameter, containing a nodal coluuinal with a 



single cirrus. Acq. No. 147. Lower part of Mendez formation. 



10. Joint-face of stem fragment 8 mm. in diameter, with petaloid sectors 



unusually small and crenate peripheral band correspondingly wide. 

 Xf . Acq. No. 271. Same horizon. 



11. Joint-face of large stem fragment, 14 mm. diameter. X|. Acq. No. 



271. Same horizon. 



