176 



C. LAPWOETH ON SOME NEW 



The hydrothecse are more prominent than those upon Dictyonema. 

 The distal extremity of each appears to have been free and slightly 

 introverted, as in the majority of the bilateral family of the 

 Dicranograptidae. 



Odontocaulis is separated from Dictyonema by the absence of the 

 transverse dissepiments, and by the polypiferous character of the 

 stem. Prom Gallograptus, which it much resembles, the same 

 features effectually distinguish it. In Dendrograptus the stem is 

 stout and devoid of polypes, while the branches are irregularly 

 disposed ; in the present genus the stem is no thicker than the 

 branches, is polypiferous, and the branches are regularly and 

 symmetrically subdivided. It has probably its nearest ally in 

 Ilhizogrcvptus (Spencer, 'Canadian Naturalist,' 1879, p. 460); but in 

 that genus the stem appears to be barren, and the branches are 

 possibly united at intervals. 



7. Odontocaulis Keepingii, sp. nov. Plate VII. figs. 7«, 7b. 



Polypary composed of numerous elegant rlexuous branches, 

 frequently divided and subdivided in a regularly dichotomous 

 manner, originating from the distal extremity of a polypiferous 

 stem about one fourth of an inch in length, and forming a 

 cyathiform frond one inch and a half in height. Hydrothecse 50 

 to the inch, free, distally patulous ; aperture prolonged, introverted ; 

 denticle obtuse, rarely spinose. 



In the only specimen collected the polypary commences proximally 

 with a flattened expansion or disk with irregular or frayed-out 

 edges. The stem is curved ventrally, and bears a single series of 

 hydrothecoe, which are most distinctly shown. There are also indi- 

 cations of a second series. These hydrothecse are a little more widely 

 separated than those upon the branches, and appear to have been 

 stronger and more projecting. At its summit the stem divides into 

 two, originating the primary branches. Within one twentieth of 

 an inch of their origin each of these again divides in a correspond- 

 ing manner. Within the next tenth of an inch the branchlets 

 are again subdivided, and so on till as many as six of these 

 dichotomous divisions have been made. The terminal branchlets 

 are very short, less than one tenth of an inch in length ; but they 

 are polypiferous to their visible extremities. 



The hydrotheca3 upon the branches average about 55 or 60 to the 

 inch. The majority are seen as scaliform impressions ; those 

 visible in profile are not unlike those in Dicellograptus, Hopkinson. 



The branches are of subequal diameter throughout, about one 

 fortieth of an inch. They are quite free and independent, neither 

 inosculating, as in some forms of Dictyonema, nor being connected 

 by transverse dissepiments, as in that genus and its ally Callo- 

 graptus. 



This beautiful little species is dedicated to its discoverer, Professor 

 Walter Keeping. 



Horizon and Locality. Llandovery of Devil's Bridge, Aberyst- 

 wyth, Cardiganshire. 



