ADDENDA. 23 



flexuous, conical, in section cylindrical, or somewhat flattened laterally, and sub- 

 triangular. Walls of the tube thick, cellular along the surface opposite to the 

 attached portion, markedly annulated along the sides. 



" Ortonia conica, Nich. — Tubes growing attached to the shell of some Mollusc; 

 varying in length from a quarter to half an inch, with a diameter of about one- 

 tenth of an inch at the mouth. Lateral annulations of the tube varying in 

 number from thirty to thirty-five in the space of an inch. Surface smooth and 

 completely destitute, so far as observed, of longitudinal striae. 



" The fossil from which the above description has been taken is an example 

 of Strophomena alternata, to the dorsal valve of which are attached the remains 

 of more than twenty individuals of Ortonia conica. In one case the tube of one 

 crosses that of another individual ; but it is quite clear that this is an accidental 

 circumstance, so to speak, and that the tubes are truly solitary. The specimen 

 is from the ' Cincinnati group ' of South-western Ohio, a formation which be- 

 longs to the ' Hudson River series,' and which corresponds with the Caradoc or 

 Bala division of the Lower Silurian. 



" In conclusion, I may add that Mr. Orton has submitted to me a beautiful 

 specimen, apparently of the Tentaculites tenuistriata of Messrs. Meek and Wor- 

 then, and also from the Cincinnati group of South-western Ohio. If this 

 specimen be rightly determined, I cannot avoid the conclusion that it is truly 

 referable to the genus Cornulites of Schlotheim, differing from the familiar Cor- 

 nulites serpularius in its small size, and in some other minor characters. This 

 conclusion, however, does not admit of complete verification except by the dis- 

 covery of specimens absolutely attached to some foreign body." 



In the Geological Magazine, vol. x, 1873, the same author publishes "Descrip- 

 tions of Two New Species of Fossil Tubicolar Annelides." He redescribes 

 the genus Conchicolites and the species C. gregarius, and describes the follow- 

 ing new species — Conchicolites corrugatus, Nich., and Ortonia minor — in the 

 following terms : 



" Conchicolites corrugatus, Nich. — Tubes growing socially in clustered masses 

 upon the shells of molluscs; calcareous; destitute of vesicular structure ; coni- 

 cal, and gently curved. Attached by their smaller extremities, sometimes for 

 the space of a line or more ; and either partially free, or contiguous to one 

 another throughout the remainder of their course. Length of the fully-grown 

 tube one-half inch or a little more; diameter of tube at mouth one- tenth of 



