ISOTELUS. 35 
them as do those of that species. The direction of the endopodites is diagonally forward, 
and the outer portions do not appear to be curved backward as in Isotclus mazimus. It 
would appear also that the endopodites were nearly or quite long enough to reach the outer 
margin of the dorsal test. On no endopodite can more than three segments be definitely dis- 
tinguished, but the longest ones are the most obscurely segmented. 
No appendages are preserved on the pygidium, but at one side of the median groove 
there are two projections which may be processes to which the appendages were attached. 
Measurements: Total length of specimen, 109 mm. Probable length when complete, 
116 mm. Length of cephalon, 40 mm.; width at genal angles, restored, about 62 mm. 
(Billings' restoration). Width of doublure of front of cephalon on median line, 17 mm.; 
length of hypostoma, 20 mm. Length of coxopodite of last appendage on left side of 
cephalon, 10.5 mm.; length of basipodite of the same appendage, 5 mm. Diameter of cox- 
opodite, 2 mm.; diameter of basipodite, 1.5 mm. Length of coxopodite on left side o.i 
the second segment of the -thorax, 11 mm.; diameter, about 2.5 mm. Length of basipodite 
of the same, 5 mm.; diameter, about 1.5 mm. Length of ischiopodite, 3.5 mm.; diameter, 
about 1.5 mm. Length of meropodite, 2.5 mm. (this may be less than the total length as 
the segment is not completely exposed.) Distance between proximal ends of gnathobases 
of the fifth thoracic segment, about 7 mm. Distance between outer ends of the coxopo- 
dites of the first thoracic segment (estimated from measurements on the left side), 27 mm 
Distance apart of the dorsal furrows at the first thoracic segment, 27 mm. Length of the 
longest exopodite which can be traced, about 20 mm. 
Isotelus maximus Locke. 
(PI. 10, fig. 2.) 
Illustrated : Mickleborough, Jour. Cincinnati Soc. Nat. Hist., vol. 6, 1883, p. 200, figs. 1-3 (endopodites 
and coxopodites). — Walcott, Science, vol. 3, 1884, p. 279, fig. 1 (endopodites, coxopodites, and traces of 
exopodites). — Woodward, Geol. Mag., dec. 3, vol. 1, 1884, p. 162, figs. 1-3 (copies of Mickleborough's 
figures). — Bernard, The Apodidai, 1892, text fig. 49. — Beecher, Araer. Jour. Sci., vol. 13, 1902, p. 169, pi. 5, 
figs. 5, 6 (outline from one of Mickleborough's figures and an original figure). — Walcott, Smithson. Misc. 
Coll., vol. 67, 1918, p. 133, pi. 24, figs. 3, 3a ; pi. 25, fig. I. 
This specimen, which comes from the Richmond strata 2 miles north of Oxford, Ohio, 
is the best preserved of the specimens of Isotelus with appendages which has so far been 
found. The individual consists of two parts, the actual specimen, and the impression of 
the ventral side. 
To describe it I am using very skillfully made plaster reproductions of both parts, 
presented to the Museum of Comparative Zoology by Doctor Charles D. Walcott, and pre- 
sumably made after he cleaned the specimen as described in Science (18S4). I have also 
an enlarged photograph (pi. 10, fig. 2) which seems to have been made after some later 
period of cleaning, probably by Professor Beecher, and I have examined the original speci- 
mens in Washington. 
Viewed from the dorsal side, it is seen that the individual is very imperfect, the greater 
part of the cephalon being removed by a. diagonal break which cuts off the anterior third 
of the left eye and extends to the front of the second thoracic segment on the right side. 
The ends of the pleura of both sides of the thorax are broken away, as are also the greater 
parts of the pleural lobes and the posterior end of the pygidium. On the ventral side, merely 
the posterior tips of the hypostoma remain, but the distal ends of the appendages were so 
far within the outer margin that the appendagiferous area is quite fully retained. 
