THE STRUCTURE OP TURRILEPAS PEACHI AND ITS ALLIES. 527 



termed Plumulites by Barrande and from the other New York species, and expresses 

 his difficulty in understanding how " the combination of these sub-conical bodies in 

 vertical ranges could produce such a scaly peduncle or capitulum as existed in Turri- 

 lepas." But T. Wrightii, the type of the genus, consists of such plates. Consequently, 

 it is obvious that much uncertainty exists as to the true reference and relations of such 

 isolated plates, and it has not been lessened by the suggestion that some properly belong 

 to Cystideans. We must wait for further and better material before we can hope to 

 clear up all the difficulties connected with these curious organisms, but it is felt that 

 with regard to T. Peachi and T. scotica we have now made some advance in the know- 

 ledge of their structure, however much it may affect our views as to their generic 

 reference and zoological affinities. 



ADDENDA. 



Since the above was written, two specimens have been sent me by Mrs Gray, which 

 probably represent the single terminal plates of the paired median series of plates in 

 both T. scotica and T. Peachi. The specimen from Balclatchie (Plate, fig. 14) shows 

 a small subcircular flattened plate with a shallow median notch in its posterior (?) 

 margin, lying near the end of a somewhat disarranged series of the usual triangular 

 plates attributed to the median series of T. scotica. The other, from Whitehouse Bay 

 (Plate, fig. 15), is a plate of similar shape, but rather more emarginate and with stronger 

 concentric striation and possessing a group of 3-4 rugse radiating from the centre to the 

 margin opposite the notch ; it may probably belong to T. Peachi. Another example of 

 the latter species from the same locality, having the anterior part of the body preserved, 

 shows that the arrangement and shape of the lateral plates at this end is the same as 

 in the figured specimen (Plate, fig. l) from the Starfish bed. In connection with the 

 occurrence of the genus as defined by Woodward, it should have been mentioned that 

 Aurivillius has recorded it from the Silurian of Gotland (Bihang till K. Svensha Vet. 

 Akacl. Handl., Bd. 18, iv., No. 3, 1892, p. 20). The genus has also been recognised by 

 the present author amongst some Silurian fossils recently collected in the Northern 

 Shan States, Burma, by the Geological Survey of India. 



EXPLANATION OF PLATE. 



Fig. 1. Turrilepas Peachi, Eth. jun. and Nich. Nearly complete individual (slightly restored). x 4. 



Starfish bed. 



„ la. „ „ „ ,, Transverse section of same specimen. 



„ 2. ,, ,, ,, ,, Median plate. x 2. Thraive Glen. 



,, 3. „ „ ,, „ Lateral plate, inner surface. x 3. Starfish bed. 



,, 3a. ,, ,, ,, ,, ,, outer surface. x 4. Starfish bed. 



„ 4. ,, „ ,, ,, Inner surface of portion of body, showing lateral and 



median plates (figured by Eth. jun. and Nich., Mon. 

 Silur. Foss. Girvan, pi. xx., fig. 8). x 5. White- 

 house Bay. 



„ 5. „ „ ,, ,, Median plate. x 3. Whitehouse Bay. 



TRANS. ROY. SOC. EDIN., VOL. XLVI. PART III. (NO. 21). 79 



