UPDATE 2-Mistras prices below range, Omeros at bottom in IPOs

* Mistras prices shares at $12.50, raises $108.75 mln

* Omeros shares priced at $10, raising $68.2 mln

* Mistras to start on NYSE, Omeros on Nasdaq on Thursday (Adds details of Omeros pricing, byline)

By Phil Wahba

NEW YORK, Oct 7 (Reuters) - Mistras Group Inc (MG.N), a provider of technology to evaluate the structural integrity of infrastructure, priced shares in its initial public offering for $12.50 per share, well below expectations.

Mistras sold 8.7 million shares in the IPO and raised $108.75 million, but the company had expected the shares to sell for between $14 and $16 apiece.

The IPO fell short despite the company's growth. The company, whose clients include Pfizer Inc (PFE.N) and ExxonMobil Corp (XOM.N), saw revenue rise 37.3 percent to $209.1 million in fiscal 2009, with net income of $5.5 million.

But it may have suffered from investors buying stocks in the massive IPOs this week by Banco Santander (Brasil) SA (SANB11.SA) SBSR.N and insurance risk specialist Verisk Analytics Inc (VRSK.O), which together raised close to $10 billion in their deals, leaving little room for new smaller stocks, advisory firm IPO Boutique wrote in a note to clients.

The IPO was managed by JP Morgan, Credit Suisse and Bank of America Merrill Lynch. The underwriters have the option to buy an additional 1.3 million shares.

About 23 percent of the shares in the Mistras IPO were being sold by existing shareholders.

The other company to complete its IPO on Wednesday -- biotech company Omeros Corp (OMER.O), which makes central nervous system anti-inflammation products -- priced its shares for $10, at the bottom of the expected range, raising $68.2 million in an IPO managed by Deutsche Bank Securities. The underwriters have the option to buy another 1.02 million shares.

Omeros has no products approved yet for commercial use and has not generated any revenue from product sales, according to a prospectus filed with regulators.

Omeros, based in Seattle, will use the net proceeds to complete clinical trials and commercialize its products.

Both stocks are set to debut on Thursday, Mistras on the New York Stock Exchange under the symbol "MG," and Omeros on Nasdaq under the symbol "OMER." (Editing Bernard Orr, Gary Hill)