432 
Aug. F. Foerste 
broader and supporting two covering plates on each side, as in the 
Ordovician species referred to Agelacrinus. 
In Lepidodiscus, as defined by Clarke, all of the thecal plates 
are squamose and imbricating, and in one species, Lepidodiscus 
alleganius, these plates are present even on the aboral surface. 
The chief feature is the essential absence of a distinct peripheral 
ring with an inner band of larger plates and an outer zone of much 
smaller plates. As in other Devonian Agelacrinidae, the rays are 
narrow. 
From typical Lepidodiscus, the Ordovician species , recently 
referred by some authors to Lepidodiscus, in preference to Agela- 
crinus, are distinguished by the presence of the distinct pe- 
ripheral band, and by broader rays. 
From this it will appear that neither Agelacrinus nor Lepido- 
discus are suitable terms for the Ordovician species hitherto 
referred to these genera, as pointed out by Clarke in 1901, and it 
will be necessary to propose a new generic term for the latter. In 
the present paper the term Agelacrinus is retained temporarily for 
the Ordovician species formerly described under that name, as 
being at least more noncommittal than Lepidodiscus, since the 
term Agelacrinus was long used in a very broad sense. 
30. Thresherodiscus ramosa, Gen. et sp. nov. 
{Plate I, Fig. 8; Plate III, Fig. 3) 
An interesting E dr io asteroid, with branching ambulacral rays, 
a feature hitherto unknown in this group of Echinoderma, was 
found by the writer, during the summer of 1912, on Goat Island, 
northeast of the village of Little Current, the chief town on Mani- 
toulin Island, Lake Huron, Ontario. The exact locality is at the 
point where the railroad from LaCloche Island strikes the north- 
eastern edge of Goat Island. Here Carabocrinus vancortlandi is 
common 7 feet above the lake level. In the overlying strata, 4 
feet thick, Plectambonites curdsvillensis occurs at various levels. 
The Thresherodiscus was found at a horizon belonging strati- 
graphically 18 feet above the lowest strata exposed at the edge of 
the lake. Here it was associated with Cleiocrinus regius, Reteo- 
crinus alveolatus, Cyclocystoides halli, and a species of Licheno- 
crinus. Between 24 and 28 feet above the lowest horizon, Glypto- 
crinus ramulosus was represented by abundant remains of the 
