234 bulletin: museum of comparative zoology. 



Stem 287 mm. long with ninety -two columnars ; the five columnars immediately 

 following the basal ring are very thin and discoidal, the sixth thicker, the seventh 

 about twice the height of the sixth ; the following segments increase in length, 

 the sixty-fourth being 4.25 mm. long and 1 mm. in diameter, and the ninety-second 

 4.90 mm. long by 1.75 mm. in greatest diameter. The columnars differ from 

 those of all known species of Bathycrinus in being practically cylindrical until 

 after the eightieth, when the articulations begin to be very slightly enlarged ; but 

 they are never markedly " dice-box shaped," as in the other species. In general 

 the stem bears a striking similarity to the stems of Rhizocrinus, the more so as 

 the thin discoidal segments at the summit are closely united so as to appear, on 

 superficial examination, as a single piece, and I had some difficulty at first in decid- 

 ing to which genus it belonged. The basal ring is large for Bathycrinus, but 

 shows no sutures whatever, even under strong magnification, nor is there the 

 slightest evidence of incorporated radials. The small number of discoidal seg- 

 ments at the summit of the stem also suggests Rhizocrinus, but in that genus 

 there are never more than two which are broader than long, and usually only one; 

 the topmost columnar in Rhizocrinus, moreover, is always considerably longer 

 than are the very thin proximal columnars of Bathycrinus. Examination of the 

 surface ornamentation of the basals and columnars shows the deep and confluent 

 pitting peculiar to Bathycrinus, and not the fine, shallow, scattered indentations 

 of Rhizocrinus. 



As an item of interest it may be mentioned that the seventeenth, fiifty-fourth, 

 and fifty-fifth columnars have the axes of both faces in the same plane ; the axes 

 are normally at right angles to each other, although occasionally the angle of 

 divergence is considerably less than 90°. 



The rapid enlargement of the proximal columnars, together with their segregation 

 into what appears superficially to be a single segment, and the cylindrical form of 

 the majority suggest an interesting possibility in regard to the original figure of 

 Bathycrinus aldrichianus. Of this figure Dr. Carpenter says : " The numerous 

 thin joints immediately beneath the cup, which are so characteristic of the genus, 

 are not properly represented in the woodcut, and the joints just below where 

 these ought to be are considerably longer than one would expect to find so near 

 the cup. It may be assumed that Mr. Wild's drawing was photographic in its 

 accuracy, so far as he could make out the structure of the small specimen ; but 

 errors may have crept in during its reproduction on wood, and the cut was pub- 

 lished during Sir Wyville's absence from England, so that he had no opportunity 

 of revising it. Under these circumstances it appeared preferable to say nothing 

 about the stem in the specific diagnosis given above rather than to attempt to 

 describe it from a probably incorrect woodcut." While in Bathycrinus australis, 

 B. carpenterii, and B. pacificus from twenty to twenty-five or even more of the 

 proximal columnars are short and discoidal, in B. gracilis and B. complanatus the 

 number is much reduced, being only about half as many or even less ; in B. 

 equatorialis only the first five are short enough to be comparable to the proximal 

 segments in the other species, and from then on the length increases rapidly. 



