The Lower Paleozoic rocks of the Shiala Formation of the Tethyan-Tibetan sedimentary sequence of Uttarakhand Garhwal region reveals rich and moderately diverse assemblages of calcareous algae. These assemblages include Dysoporelleae, Cyclocrinitids, Solenoporaceans, Microproblematica and cyanobacteria. Seven species have been identified. Most of the taxa described here are reported for the first time from the Shiala Formation. This formation exposes six different microfacies types. Some of the calcareous algal association occurs in different microfacies types and they are not generally facies dependent. The presence of calcareous algal age marker forms in the Shiala Formation brackets the upper age limit as Silurian and it is consistent with earlier age as assigned by acritarch biostratigraphy. The recovered flora is broadly comparable with that of the Tarim basin of China, Uzbekistan, Ontario, Scotland, Kazakhstan, Poland, Baltica etc. A possibility of regional link between the present study area and Tarim basin during Ordovician-Silurian time can not be envisaged based on floral similarity of the two basins due to their cosmopolitan affinity in Gondwana, Laurentia, Siberia, Kazakhstania etc. The recovered flora is basically from the euphotic zone(within few dozen meters) of coastal to lagoonal, low to high energy marine waters of deposition in a tropical to warm-temperate palaeoprovince of Ordovician-Silurian time.

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Melanosclerites, a little-known group of organic microfossils, are recorded for the first time from the Lower Silurian Wilhelmi Formation, Illinois, USA. The taxa described herein include Melanorhachis regularis

Well preserved pleuridia attributed to the problematic group known as melanosclerites have been discovered in Upper Ordovician greenish-grey silty shales of the Shiala Formation of the Tethyan Garhwal Himalaya of India. This material is attributed to genus Melanosteus, which has also been reported from Ordovician and Silurian erratic boulders of the Baltic region, as well in Devonian Upper Gaspe Limestones from the Gaspe Peninsula, Canada. The new species Melanosteus indica comes from below the Ordovician-Silurian boundary as established by acritarchs from the same section.